A Carro di Rottura (breakthrough tank) was to be developed.
Fiat-Ansaldo built it as a Carro di Rottura. It was developed as the 8 T in 1932 but was changed to M 11-39 in 1937.
In 1937 prototype was built. The Regio Esercito (Royal Italian Army) placed an order for 100 of them in 1938. Production was nine per month.
Started with 6 road wheels and was similar to American M3 Lee except had 37 mm in sponson. Eventually had 8 road wheels. Initially had an RF 1 CA radio, but production models had no radio.
Had 2 Breda 8 mm machine guns in the turret and a 37 mm mounted on the right side of the hull. The driver was on the left side.
The 37 mm gun had a telescopic sight. The two 8 mm Breda machine guns were in a cast gimbal mount with a telescopic sight and room mounted periscope.
On each side of the hull superstructure were oval pistol ports. There were two ports in the right rear superstructure.
Entrances were in the turret room, above the main gun, and a door in the left side.
The armor was bolt-on plating. Riveted construction.
Air intakes were at the rear in the superstructure and the turret.
The driver was located on the left towards the front of the M11/39. The commander was the only one in the turret which was located in the center of the M11/39.
The engine was in the rear with the drive going to the front sprockets. The adjustable idler was in the rear.
There were two radiator gills at the rear of the engine compartment.
The suspension had two four-wheel bogies mounted in pairs on a semi-elliptic leaf spring.
It had four double wheeled articulated bogies that were paired into two bogie assemblies. They were carried on semi-elliptical leaf springs.
Two spare bogie wheels were fitted on the rear hull, with the jack on the front left fender.
A company in the 32nd Tank Regiment of the Ariete (Ram) Armored Division received the first batch to test in August 1939.