What is beyond question is that a military revolution occurred between 1914 and 1918. It began with infantry equipped with rifles trained to fight in line, supported by a few machine-guns and rather more ample field artillery, and with large contingents of cavalry available for reconnaissance and pursuit. It ended with combined-arms warfare based on small infantry squads equipped with machine-guns, mortars, grenades, and rifles, backed by concentrated heavy artillery and hundreds of tanks and aircraft.

The Germans were the first to develop new ‘shock-troop’ and ‘infiltration’ tactics – precursors of what would later be called Blitzkrieg – but it was the Allies on the Western Front (British, French, and American) who brought the new way of war to its highest level during the Hundred Days Offensive at the end of the war. They had the industrial resources to provide the machines necessary to break the deadlock and restore movement to the battlefield.

Airpower evolved in this context from a questionable reconnaissance role in 1914 (when many generals still insisted that cavalry were more useful) to multiple roles in 1918, including, in addition to fast reconnaissance, strafing and bombing in support of ground operations, attacks on rear areas, pursuit, and air-supply.

At the same time, however, the Germans mounted a strategic bombing campaign over Britain, first using Zeppelin airships, then, with greater effect, a new generation of aeroplane bombers, the Gothas and Giants.

The British responded in kind, especially after the creation of the RAF and the appointment of Hugh Trenchard to command it.

Was the diversion of resources worth it? Or would it have been better to have invested more heavily in the development of airpower in a tactical role?

Neil Faulkner takes up these and other questions in our special this time. He looks first at tactical operations, then at strategic bombing, in this second part of our occasional series on the development of airpower in war.

Tactical Operations

Airpower in wartime is a technological and industrial arms-race. On the one hand, designers are constantly at work to improve performance and gain an advantage over enemy machines. On the other, aircraft must be mass-produced – and new pilots trained – to match urgent demand and heavy attrition at the front. These two aspects of air war – technological change and mass-production – are in contradiction.

A First World War fighter typically comprised 50,000 parts and required 4,000 man-hours to assemble. It was a complex precision machine that was 100% hand-built.

Even during the Second World War (and later), aircraft manufacture proved less amenable to assembly-line production methods due both to the complexity of the machines and to the pace of design modifications.

Aircraft manufacturers during the First World War were also grappling with conflicting design requirements. Was the priority safety or performance? Stability or speed? Manoeuvrability or load-bearing?

And they were under constant pressure to work fast. Should a new engine be installed even without comprehensive testing? Should a new design go into production even with minor faults unaddressed?

Similar pressures affected pilot training. With both a huge increase in air forces and severe attrition, pilot training became an industry in itself, with training aerodromes a mushroom development on the home front.

France had begun the war with 134 trained pilots. By the end, she was training five times that number every month, ending the war with 18,000 military pilots.

The cost was huge. The British estimated that it cost them $25,000 to train a pilot, more than five times the cost of a fighter aircraft.

The attrition in training was heartbreakingly high, with one crash fatality a month at many aerodromes, largely due to the speeding up of the training process under wartime pressure.This was compounded by heavy losses at the front, as under-trained and inexperienced pilots were sent into action before they were ready. In just 18 weeks on the Somme, the Royal Flying Corps suffered a 100% casualty rate. The Western Front consumed pilots as voraciously as infantry.

Knights of the air

The survivors were a special breed. They were a new kind of military elite. ‘Flying is not now confined to the public-school boy, the cavalry officer, or the athlete,’ it was reported in the authoritative British medical journal The Lancet. ‘We take many of our pilots at present from the lower middle classes and some from the artisan class.’

This would remain the case, with distinctions of background and rank counting for less among airmen than among other military. Ground crew had to be skilled mechanics. Pilots needed, in addition to training, steady nerves, a certain recklessness, even, it was said, ‘a lack of imagination’ – an ability to shut out the horrors of death in the sky and close on an enemy to make a kill.

The realities were grim. The odds were no better than for infantry in trench warfare on the ground. As well as 1,000 killed in training, the British lost more than 4,000 pilots (out of 22,000) during the First World War.

Many died gruesome deaths. What all airmen feared most was to be set on fire. Some chose to jump from a stricken machine to avoid this fate. Others were hit by explosive and/or incendiary bullets. One American survivor recalled a narrow escape:

An explosive bullet hit me in the left cheek and knocked out 16 teeth, breaking both jaws and then tearing through the windshield, breaking it also. I remembered spitting out teeth and blood, and turned again for our lines… Two more explosive bullets hit me in the left arm, tearing through and breaking the left elbow. Two broke in the right hand and nearly took off the right small finger. Another hit me in the left thigh, one in the left ankle, and one in the right heel. Six of the ten wounds were from explosive bullets…

Even pilots who avoided injury risked frostbite from the bitter cold in open cockpits, dizziness and blackouts from lack of oxygen, and sickness induced by the oil and fumes spewing from engines, petrol tanks, and fuel lines.

Only a few men in each squadron proved to be effective killers: the necessary combination of cool, skill, and fearlessness was exceptional even among pilots. (The same, of course, was true of war in general.) Many of the aces were perhaps touched with madness. Some seem to have become drunk on thrill and blood.

But all shared in the glamour, for pilots were lionised by news media hungry for stories of ‘heroes, ‘gladiators’, ‘knights of the air’ in a war dominated by murderous attrition in the mud of no-man’s land. The top aces became celebrities whose names were known to millions.

A military revolution

The increasing mass of airpower – the British and the French each manufactured 50,000 aircraft in the course of the war – was one feature of a military revolution born of the trench stalemate of 1915-1917. The great offensives at Verdun, the Somme, and Passchendaele in particular had taught sharp lessons. And while manpower had peaked in 1916, machine-power – the numbers of guns, tanks, aircraft, lorries – continued rising to the end of the war.

Labyrinthine defensive complexes and the ‘storm of steel’ in no-man’s land had rendered massed assaults by lines of rifle-armed infantry suicidal. The demand was for ever more machines: light machine-guns and mortars to equip semi-independent squads of infantry; artillery to smash strongpoints and suppress hostile fire; tanks to punch a hole in the enemy line; lorries to feed rations, ammunition, and men into an advance; aircraft to locate, strafe, and bomb enemy positions.

Air doctrine evolved as one dimension of a new way of war that was designed to end deadlock and restore movement to the battlefield.

Infantry were to break down into small groups and go to ground; they were to get forwards by folding themselves into the landscape; they were to be self-reliant and proactive; they were to ‘infiltrate’ themselves into the deep defensive complex of the enemy trench-system.

Artillery was to be massed in unprecedented concentrations and used to create such a tempest of explosive and shrapnel ahead of the attack that no effective resistance would be possible.

Tanks would no longer be scattered along the front, but combined in iron fists of 25 or 50 machines to make a breach for the infantry.

And it was now that airpower came of age, especially in the final Hundred Days Offensive on the Western Front between 8 August and 11 November 1918.

Military aviation was now being used in a full range of tactical roles. As well as reconnaissance, reconnaissance escort, and reconnaissance interception, aircraft were now used: in air-to-ground strafing and bombing in close association with infantry; in widespread attacks in rear areas on artillery emplacements, assembly areas, roads and bridges, railways, supply depots, and command-and-control centres; and in aerial resupply, dropping ammunition and rations to troops otherwise cut off.

The Battle of Le Hamel

The Battle of Le Hamel on 4 July 1918 was a model of the new ‘scientific’ approach to war. The architect was Lieutenant-General John Monash, commander of the Australian Army Corps, a man determined not to see his country’s manpower ‘wither away under merciless machine-gun fire, nor to impale itself on hostile bayonets, nor to tear itself to pieces in hostile entanglements’. His alternative was

to advance under the maximum possible array of mechanical resources, in the form of guns, machine-guns, tanks, mortars and aeroplanes; to advance with as little impediment as possible; to be relieved as far as possible of the obligation to fight their way forward; to march, resolutely, regardless of the din and tumult of battle, to the appointed goal; and there to hold and defend the territory gained; and to gather, in the form of prisoners, guns, and stores, the fruits of victory.

This required meticulous planning, for it was necessary to combine the work of infantry, artillery, armour, and airpower in a precise choreography. Monash was the man: a new type of machine-minded general whose conduct of battle was more akin to the management of an industrial firm than to the art of war of the great captains of the past.

The defenders never had a chance. Everything went like clockwork and it was all over in an hour and a half. British GHQ reported that success was due to ‘the care and skill as regards every detail with which the plan was drawn up’ and ‘the excellent cooperation between the infantry, machine-gunners, artillery, tanks, and RAF’.

This included, as military historian John Terraine records, a notable battle- field improvisation:

An important feature of consolidation in any advance was the rapid advance of the machine-guns to the captured positions; but it was not just the guns that had to go forward – they needed ammunition, and machine-guns devour ammunition in vast quantities. At Le Hamel, for the first time in history, a solution to this serious problem was attempted by air supply, and the RAF successfully dropped 100,000 rounds to the Australian machine-gunners during the battle…

The Battle of Amiens

The tide turned on the Western Front at the Second Battle of the Marne (18 July-3 August 1918), and a full-scale Allied offensive was then launched on 8 August.

The attack on this first day, remembered as the Battle of Amiens, turned into a decisive Allied victory – Ludendorff described it as ‘the black day of the German Army in the history of the war’. Fifteen miles of enemy front was broken, 400 guns were captured, and almost 30,000 Germans were killed, wounded, or, in the majority of cases, taken prisoner.

The assault force had been a sledgehammer of industrialised military power: ten divisions of infantry, 500 tanks, more than 2,000 guns, almost 2,000 aircraft.

As the morning mist cleared, ‘the whole Santerre plateau seen from the air was dotted with parties of infantry, field artillery, and tanks moving forwards’. And then the great Allied air fleet came into action and ‘the battlefield became alive with aeroplanes’. As Terraine describes:

Low-flying aircraft attacked machine-gun posts, stampeded horse-drawn transport, shot up staff cars, and scattered infantry formations – all this adding greatly to the strain on German nerves.

At midday, there was a switch to attacks on bridges in the German rear as reports came in that the roads were congested with retreating troops and transport. Perhaps the German Second Army could be trapped and destroyed.

This provoked a furious German aerial reaction. The threat to their army forced them to commit their heavily outnumbered squadrons – with fewer than 400 aircraft available – in an effort to defend the line of retreat. In effect, they sacrificed the air force to save the army. The British Official History records that the German pilots

fought generally with a reckless courage to take toll of the bombers, even though they could not prevent the attacks… The only means by which the German fighter pilots could redress in some degree their inferiority in numbers was to spend the minimum time upon the ground. Many of them were in the air on 8 August for ten hours, taking part in combat after combat.

Among the squadrons involved was the famous ‘Circus’ of the Red Baron, now commanded by one Hermann Goering, ‘a leader of proved worth’ who

was possibly gifted with a temperament more offensive in quality than that of his predecessor, or it may be that the German air service, sensing that the whole background of the war was changing, was impelled to throw its weight into the battle heedless of danger or cost.

It was one of the most ferocious air battles of the First World War, this struggle for air supremacy over the German Second Army’s escape-route. The Richthofen Circus was virtually destroyed, along with many other German squadrons, but the RAF lost 45 aircraft shot down and a further 52 so badly damaged they had to be written off.

The Battle of St-Mihiel

The first American operation of the war, the Battle of St-Mihiel on 12 September, was another triumph of planned machine warfare. The assault, by more than half a million Doughboys, backed by more than 100,000 Frenchmen, was supported by 3,000 guns, 1,400 aircraft, and 270 light tanks.

By late morning, the main attack had secured its three objectives and bagged 15,000 prisoners and 460 guns. This represented the advent of US military aviation, led by an irrepressible self-promoter called Billy Mitchell. The service was in its infancy. Despite strenuous efforts to manufacture US planes, the design and manufacturing experience was not in place, so virtually all the planes flown by American pilots were French-made. The Americans also needed support from French and British squadrons. And they suffered heavy losses at the hands of the formidable Fokker D.VII.

Nonetheless, the contribution of airpower to the victory was substantial. Allied aircraft launched devastating attacks on German columns on the roads behind the front. ‘Dipping down at the head of the column,’ recalled US ace Eddie Rickenbacker of one such attack,

I sprinkled a few bullets over the leading teams. Horses fell left and right. One driver leaped from his seat and started running for the ditch. Halfway across the road he threw up his arms and rolled over upon his face. He had stepped full in front of my stream of machine-gun bullets. All down the line we continued our fire… The whole column was thrown into the wildest confusion. Horses plunged and broke away. Some were killed and fell in their tracks. Most of the drivers and gunners had taken to the trees before we reached them.

The future of military aviation

Mass, technology, doctrine: all three developed fast in the last year of the First World War. Though airpower played only a limited role in the German offensives of March-July 1918, it was an increasingly important component of the combined-arms tactics of the Allies in the final Hundred Days Offensive.

Aircraft were being used in four classic tactical roles – intelligence, bombardment, pursuit, and resupply – and this gave rise to a new kind of fighting: air-to-air combat to achieve air supremacy.

Aircraft had replaced cavalry as the basis for long-range observation and intelligence-gathering. They acted as ‘mobile artillery’, supplementing the work of ground artillery by offering immediate, highly targeted, close-range support for infantry attacks. They were then available to follow up success by fulfilling another traditional cavalry role, that of pursuit, and sometimes to do so with devastating effect.

Then there was air resupply. Ammunition had been dropped at Le Hamel on the 4 July. ‘On 2 October there was another portent,’ reports John Terraine,

news came that leading Belgian and French formations had exhausted their food supplies, and 80 aircraft… airlifted 15,000 rations to these troops. The rations were packed in batches of five or ten in small sacks of earth carried in the cockpits of aeroplanes. These were thrown out at a height of about 300 feet: the earth cushioned the impact so that the rations were undamaged. The total amount dropped was 13 tons, a ludicrously small quantity… but everything has to have a beginning.

Strategic Operations

On 13 June 1917, a German bomb went through the roof of the London County Council School in Upper North Street, Poplar, dropping through two storeys before exploding in an infant classroom. Eighteen five-year-olds were killed and a further 37 people injured.

This was a new and terrible kind of war: the first time in history that civilians on the home front had been deliberately targeted by aerial bombing. The popular press denounced ‘the Huns’ as ‘baby-killers’. The funeral of the dead children from Upper North Street School was one of the biggest in the history of London’s East End.

Anger mixed with fear. There were anti-German riots in some cities; shops with German-sounding names were attacked. Men in Royal Flying Corps uniform were abused in the street for letting the bombers get through.

Thousands spent sleepless nights sobbing and trembling, expecting the bombs to fall at any moment, even when no air-raid was in progress. Tens of thousands crowded into basements and underground stations.

On the night of 28/29 January 1918, a huge bomb landed outside a printworks in Covent Garden, in the basement of which some 500 people were sheltering. The blast caused part of the building to collapse and the rest to catch fire. Two of the three basement exits were blocked. Thirty-eight were killed in the disaster. The screams of those trapped beneath the rubble of burning buildings would haunt those who heard them ever after.

To bomb or not to bomb?

For many advocates of strategic bombing, this had always been the intention. Peter Strasser, commander of the German Naval Airship Division, spoke of ‘the dread of air- ships prevailing in wide strata of society’. His superior, Rear-Admiral Paul Behncke, was more explicit:

[air raids] may be expected… to cause panic in the population which may possibly render it doubtful that the war can be continued… In general, air attacks with aeroplanes and airships… promise considerable material and moral results. They must therefore be considered an effective means of damaging England.

This, of course, had been the stuff of pre-war sensationalist journalism and science-fiction. The outbreak of the First World War brought popular fears to a head. But, at first, the bombers did not come.

There were many reasons. Larger bomber forces did not exist in August 1914. Debate still raged over whether to prioritise airships or aeroplanes. The war of movement on the ground seemed to promise a quick victory. There were political reservations about the bombing of cities and civilians, mainly for fear of moral opprobrium and retaliation in kind.

The Kaiser, in particular, was squeamish. He refused to order any air-raids on Britain until 10 January 1915, and unrestricted aerial bombing was not permitted until 20 July. What drove this change was the inexorable logic of total war.

When the war of movement on the Western Front ended in November 1914, a war of attrition began, one in which industrial output and civilian morale counted as much as the outcome of great battles. The British naval blockade was soon damaging German industry and affecting civilian food-supplies. Unable to break the stalemate and threatened with slow strangulation, Germany’s leaders turned to the magicians of wonder-weapons.

Zeppelin raids

Doubts remained over whether the future of flight lay with aeroplanes or airships; and the demand for aeroplanes on the fighting fronts was such that, initially, the Germans turned to airships to mount a strategic bombing campaign.

An airship was a huge lightweight framework of Duralumin girders and steel wires supporting a row of gas-bags made of animal membrane, cotton fabric, and glue, which, when inflated with hydrogen gas, filled almost the entire inner space. Stretched over the exterior of the framework was an envelope of light cotton fabric, coated in dope, laced together, and pulled taut.

The keel of the Duralumin framework formed a gangway running the length of the ship, and here were stowed water-ballast sacks, petrol tanks, and bomb racks. Slung beneath the keel were a forward control gondola and one or more engine gondolas, which powered propellers. Direction was controlled by cables that ran from the forward gondola to movable rudders and elevators attached to tail-fins.

Airships – or Zeppelins – were bigger than battleships, triumphs of modern engineering, and a sinister black presence in the night sky threatening death and destruction to those below.

But the problems with the weapon system were numerous. Airships were operationally dependent on good weather, clear skies, favourable winds, and the darkness of long, moonless nights: ideal ‘Zepp nights’ were few.

Aerial navigation was in its infancy and relied on a haphazard mix of dead reckoning, radio signals, and direct observation of the ground below. Airship captains rarely knew their location with any accuracy, and sometimes could be hundreds of miles out.

Even if they found their way, targets were hard to identity, bombsights crude, and it was pure chance whether a bomb struck any sort of military installation. On the other hand, carpet bombing was not an option, because the airships were too few and their bomb-loads so minimal.

Adding to the problems was the effect on the crews of head-splitting roar, and of an asphyxiating mix of oil and exhaust fumes in the engine gondolas and bitter cold, sinking as low as −25°C, in the control gondola.

When a new generation of ‘height-climbers’, which cruised up to four miles high, was introduced – designed to escape thickening British home defences – crews were further afflicted with acute oxygen shortage and suffered headaches, nausea, exhaustion, and blackouts.

Thus, despite the hype, in both Germany and Britain, there were only 53 airship raids between January 1915 and August 1918, during which a mere 6,000 bombs were dropped, total casualties were 1,900, and total damage estimated at around £1.5 million (a quarter of what Britain was spending each day on the war).

Home defence

Not the least problem was the exceptional vulnerability of an airship. What was it but a huge, slow-moving balloon of explosive gas, liable to be transformed in an instant into a blazing inferno?

But this depended on the development of an effective home-defence system. This took time to improvise. The British began this particular technological arms-race at a virtual standing start, with just 37 anti-aircraft guns, most of them useless, to defend the entire country.

Guns, anyway, defend fixed positions (even mounted on trucks, as many were, they could not actually pursue the raiders). Only aeroplanes could engage in a battle for air supremacy by hunting and destroying airships. But to have a chance of bagging their quarry, there needed to be enough of them alerted to a raid and searching the sky, ideally aided by searchlights on the ground, and they needed to be equipped with an effective weapon.Only in the autumn of 1916 did the British home defence achieve the critical mass necessary to tip the balance against the raiders: an early warning system to alert the defenders; a ring of lights and guns that kept the attackers corralled in a killing zone around London (their primary target); a sufficient number of fighters to patrol this zone, manned by pilots trained in night flying and committed to hunter-killer tactics; and a new explosive and incendiary ammunition (a combination of the two designed to burst the bags and ignite the gas).

The result was four Zeppelins shot down over Britain in a month, a turning of the tide the Germans never succeeded in reversing, despite the new generation of ‘height-climbers’.

But London’s ‘first Blitz’ was not over.

Gothas and Giants

The Germans had been developing a new heavy bomber – the Gotha – which, by late spring 1917, had been perfected, mass-produced, and formed into an ‘England Squadron’. The first mass raid – by 23 bombers on 25 May 1917 – came as a shock.

The Gotha was a large, twin-engine bomber, with a maximum speed of 80mph, a maximum ceiling of 15,000ft, and, crucially, a maximum range of 500 miles. Each was manned by three men – a commander-navigator (and bomber), a pilot, and a rear-gunner – and, in addition to bombs, the plane carried a defensive armament of three machine-guns.

Flying in tight V-formations, the Gothas’ combined firepower made them highly dangerous targets for fighters – so much so that more Gothas were lost to accidents than to enemy action.

In September 1917, yet another new weapon entered the fray: the Zeppelin-Staaken ‘Giant’, a six-engine monster twice the size of a Gotha and carrying four times the bomb-load. Manned by up to nine men and defended by up to seven machine-guns, the Giants were in fact bigger than any German bomber of the Second World War. One machine was powerful enough to fight off an entire swarm of fighters, and not a single Giant was lost to enemy action.

It was the buckling of the German economy in the last year of the war that put paid to the strategic-bombing campaign, not the effectiveness of the British defence. The diversion of resources was judged not worth the effort.

Was the German bombing campaign effective?

Despite the greater effectiveness of the Gothas and Giants as strategic bombers, the direct effects of the German air offensive remained modest: around 5,000 casualties and £3 million of damage in total. But these were not the effects that mattered: it was the indirect ones – disruption and diversion. For one thing, the combination of blackouts, shutdowns, and absenteeism had a huge (though incalculable) effect on war production. For another, popular clamour forced a substantial diversion of military resources to home defence: an eventual total of 17,000 men, 470 guns, 620 searchlights, and 380 aircraft. Third – and perhaps most significantly – resources were diverted into retaliation.

The bill establishing the RAF and setting up an Air Ministry was passed with minimal debate in Parliament on 29 November 1917. Major-General Hugh Trenchard was appointed Chief of the Air Staff in January, and the Royal Flying Corps and Royal Naval Air Service were formally amalgamated into the Royal Air Force on 1 April 1918.

This was, in effect, a decision to create a strategic-bombing force. As such, it was a political decision arising from the popular demand for retaliation for German air attacks. The Gotha raids created the RAF.

This was more or less explicit in General Smuts’ official government report, which recommended both an all-out strategic bombing campaign against Germany and the establishment of an independent air force. ‘As far as can at present be foreseen,’ he reported in the light of the Gotha raids,

there is absolutely no limit to the scale of its [the air arm’s] future independent war use. And the day may not be far off when aerial operations with their devastation of enemy lands and destruction of industrial and populous centres on a vast scale may become the principal operations of war, to which the older forms of military and naval operations may become secondary and subordinate…

Smuts predicted continuing stalemate on the ground and opined that ‘the air battle front’ and ‘its continuous and intense pressure against the chief industrial centres of the enemy as well as on his lines of communication may form the determining factor in bringing about peace.’

The British strategic-bombing campaign

Trenchard concurred, and some of the military history of the summer and autumn of 1918 comprised a tussle over priorities between a cantankerous bomber chief and the army high command. The former’s response to evidence that strategic bombing was ineffective and that, as the French put it, ‘one does not bomb just for the sake of bombing’, was similar to that of independent bomber commanders right through the next century:

Actual experience goes to show that the moral effect of bombing industrial towns may be great, even though the material effect is, in fact, small.

The anxiety as to whether an attack is likely to take place is probably just as demoralising to the industrial population as the attack itself.

In other words, Trenchard was advocating terror bombing of cities and civilians, and he was arguing that this was a more efficient use of airpower than tactical deployment in combined-arms operations on the main battlefronts.In fact, ‘actual experience’ showed the opposite. The British General Staff had carried out a detailed analysis of the effects of aerial bombing in July 1915. Reviewing the results of 483 operations, they concluded that of 4,000 bombs dropped, almost none had hit anything. Among 991 bombs dropped in 141 of those operations, only three appeared to have hit a military target. Even when a significant target was hit, the consequences tended to be limited. Damage to railway tracks, for example, could usually be repaired in a matter of hours. One RAF study concluded that even if a 112lb bomb scored a direct hit on a railway line, it would cut only one rail, and this could be replaced by a party of ten men in an hour and a half.

This was confirmed by the investigations of Henry Tizard, an Oxford chemistry boffin recruited into the war effort, who calculated that the destruction of one German chemical factory would require 2,500 bombs – the equivalent of 1,000 sorties by DH4 bombers. When his reports were ignored, Tizard drew the inevitable conclusion: the purpose of strategic bombing was not ‘a serious attempt to end the war’, but ‘to keep our own unenlightened populace quiet’.

A technological impasse

There were multiple problems. The Handley Page, Britain’s twin-engine heavy bomber, could carry a ton of explosive but was painfully slow; a more powerful four-engine model was not available for service before the end of the war.

The smaller DH4 could carry only a few hundred pounds, and the FE2 pusher was nothing more than an obsolete fighter pressed into service as a light bomber. Problem 1, then, was that Trenchard lacked the mass for a strategic-bombing campaign.

This meant, of course, that carpet bombing of cities and civilians – to induce large-scale disruption and panic – was not an option, irrespective of questions around its efficacy.

But nor did he have the technology to carry out precision bombing of key targets. No one yet fully understood the physics of aerial targeting, and the bombsights available were so crude as to verge on useless.

The technical problem to be solved was hugely complex, with numerous variables: the height of the aircraft, the speed of the aircraft, the weight of the bomb, the atmospheric conditions, and more.

This was assuming that the aircraft had been successfully navigated to the target area in the first place, and that the bomb-aimer had been able to see and correctly identify the target below. Whereas, one British report noted in September 1917,

Experience has shown that it is quite easy for five squadrons to set out to bomb a particular target and for only one of those five ever to reach the objective, while the other four, in the honest belief that they have done so, have bombed four different villages which bore little if any resemblance to the one they desired to attack.

All this before taking any account of possible enemy defensive measures – ground fire and fighter interception.

Trenchard was undeterred to the end. In September and October 1918, he was directing 85% of his bombing missions against railways and airfields. He considered expert opinion on the matter to be an irritating distraction.

This would prove a recurring pattern. With the numbers and capabilities of bombers increasing over time, the advocates of strategic bombing would always be able to argue that, despite disappointing results in previous campaigns, the necessary power had now been assembled to force a decision. And because the actual effects of a bombing campaign were always clouded in the fog of war, hidden on ‘the other side of the hill’, it was never possible to be sure.

The debate over air-war priorities – combined-arms tactical operations or independent strategic-bombing campaigns – would therefore run and run.

This article draws heavily on three main sources: Stephen Budiansky’s excellent Air Power from Kitty Hawk to Gulf War II: a history of the people, ideas, and machines that transformed war in the century of flight (Penguin); John Terraine’s To Win a War: 1918, the year of victory (Papermac); and Jack Herris and Bob Pearson’s The Essential Aircraft Identification Guide: Aircraft of World War I, 1914-1918 (Amber Books).
All images: WIPL; Amber Books