On their own initiative, the Kirov factory has been working on a new heavy tank since the middle of 1943 (Object #701).
On April 6th, 1944, letter #5-1881s was sent to comrade Stalin, signed by comrades Beria, Malyshev, and Fedorenko with a request to approve the attached project of a GOKO decree, allowing the Kirov factory to begin building experimental prototypes of the new tank.
On April 8th, 1944, GOKO decree #5583ss was issued, allowing the NKTP to produce two experimental heavy tanks in April and perform trials with GBTU.
The Kirov factory produced the tanks and presented them for trials.
From June 28th, 1944 to July 30th, 1944, the Commission appointed by order #368/01 of the NKTP and Commander of the Armoured and Motorized Forces issued on June 3rd, 1944, began trials of the two experimental prototypes of object #701 (Lieutenant-General of the Tank Forces comrade Vershinin's Commission).
Trials showed that a series of components (final drive, gearbox) need improvements.
In his order #500s issued on August 11th, 1944, the People's Commissar of Tank Production comrade Malyshev instructed the Kirov factory to introduce improvements to the experimental prorotypes in accordance with the comments made by the commission and present the prototypes for secondary trials.
The results of the trials were reported to comrade Beria in letter #5-4513s signed by comrades Malyshev and Fedorenko on August 11th, 1944.
The Kirov factory improved the experimental prototypes and sent them for secondary trials.
Secondary trials were held at the NIBT proving grounds from December 17th, 1944, to January 24th, 1945. The commission appointed by the Commander of Armoured and Motorized Forces recommended the tank for adoption by the Red Army.
On February 8th, 1945, the Chair of the Commission, Engineer-Colonel comrade Blagonravov, reported the results of the trials to the Armoured and Mechanized Forces Council.
The Council decreed that:
- Report to the Government regarding the adoption of the new heavy tank (Object #701) into the Red Army and organization of its production at the Kirov factory as a part of the main tank and SPG production program.
- Approve the report of the Commission regarding the experimental prototypes.
(Excerpt from the minutes of meeting #4 of the Armoured and Mechanized Forces Council on February 8th, 1945)
On February 11th, 1945, letter #836878 by the Armoured and Mechanized Forces Council reported to comrade Beria of the trials and asked for his approval regarding accepting the new tank into service.
Due to the fact that the People's Commissar of Tank Production, comrade Malyshev, insisted that the tank should be tested in difficult road conditions, a letter was written in March of this year to comrade Beria signed by comrades Malyshev, Korobkov, Biryukov, and Zaltsmann with a proposal to perform additional trials of Object #701 and simultaneously allow the Kirov factory to begin preparing for production of the new tank.
According to order #135/0029 of the NKTP and Commander of the Armoured and Motorized Forces issued on March 22nd, 1945, the supplementary trials of Object #701 were conducted. One prototype that previously travelled 1451 km was tested at the NIBT proving grounds over an additional 307 km. The second prototype was being tested in Chelyabinsk and travelled 686 km. Trials were conducted off-road in conditions of spring mud.
Results of the additional trials were sent in memo #1658 dated May 5th, 1945 from the Chief of the Tank Directorate to the Deputy Commander of the Armoured and Mechanized Forces, Colonel-General of the Tank Forces, comrade Korobkov.
Currently, the prototype of the new heavy tank with a new turret with thicker armour and a coaxial DShK machinegun is located at the NIBT proving grounds."