Back to the Drawing Board: the M11/39 Medium Tank

DAVID PORTER ON MILITARY HISTORY’S DOOMED INVENTIONS

Mussolini’s ambition to create a new Roman Empire was constantly undermined by Italian war industries, which were totally inadequate to mass-produce the necessary modern weapons. This was especially true of Armoured Fighting Vehicles (AFVs). By the mid-1930s, the Italian army could still field nothing more than obsolete armoured cars and tiny tracked L3 machine-gun carriers, often referred to as ‘tankettes’ in contemporary publications.

The Italian M11/39 during the Western Desert Campaign, September 1940. The type’s limitations rapidly became apparent after Italy entered the war, and it was quickly phased out. Image: Wikimedia Commons

A requirement for a new 10-ton medium tank was finally issued in 1936, and the prototype M11/39 was completed two years later. The design was heavily influenced by the Italian campaigns of the 1930s, such as the conquest of Ethiopia, when the limited arc of fire of the L3 machine-gun carrier led to several vehicles being destroyed by flank and rear attacks launched by infantry anti-tank teams with improvised demolition charges.

Subsequent combat experience in the Spanish Civil War had shown the urgent need for the new design to incorporate an effective anti-tank gun. In several actions in Spain, the machine-gun-armed L3s were found to be helpless against Republican T-26 tanks with their 45mm guns.

These factors led to the decision to fit a machine-gun turret while mounting the 37mm Vickers-Terni L/40 main armament in the hull front to keep the weight within design limits. The 37mm gun was powerful enough to deal with most contemporary AFVs, but its traverse was limited to only 30°, even though the secondary weapons – twin 8mm Breda machine-guns – had full 360° manual traverse. (A total of 2,808 rounds were carried for the machine-guns, whose effectiveness was limited by their 24-round box magazines, each of which held enough ammunition for barely four seconds of continuous fire.)

Strengths: effective 37mm gun
Weaknesses: limited-traverse main armament, poor internal layout, thin armour

Cramped layout

The internal layout was poor, with the commander isolated in the cramped one-man turret, while the two remaining crew members – gunner and driver – sat side by side in the hull. A contemporary Australian report on captured vehicles noted that ‘the hull gunner is a very cramped position and in danger of being hit by the turret (traversing) mechanism. Commander in a cramped position and dangerously near the recoiling breach of the 37/40 gun.’

The type’s limitations rapidly became apparent after Italy entered the war in June 1940. Of the 100 available, 72 equipped the Ariete Armoured Division in Libya, where they faced the light, cruiser, and infantry tanks of the British Western Desert Force.

Early action showed that the M11/39’s thin side and rear armour was vulnerable even to the .5-inch Vickers machine-guns of British light tanks. It was also found that, although the 37mm Vickers-Terni could penetrate British light and cruiser tanks at normal battle ranges, its limited traverse put the M11/39 at a significant disadvantage in combat against British tanks armed with the more powerful 40mm 2-pounder gun in fully traversing power-operated turrets.

Worse, the heavily armoured Matilda II infantry tanks were found to be completely immune to the Italian gun even at point-blank range.

It was clear that the M11/39 was hopelessly outclassed, and from October 1940 the type was phased out of service in favour of the far better M13/40 medium tank.