"To the Central Committee of the VKP(b)
Comrade I.V. Stalin
People's Commissar of Defense of the USSR, comrade K.Ye. Voroshilov
Bolshevik fighters and commanders of the Ukrainian Military District, enthusiasts of mastering and further perfecting our powerful combat vehicles, report this to you.
Your directions in improving the drive of the BT tank is complete. We present to you a new type of drive for BT tanks.
The new wheeled drive powers not one, but three (2nd, 3rd, 4th) pairs of wheels. Three pairs of wheels (1st, 2nd, 4th) can also be used to steer, instead of just one. The blueprints for this new vehicles are complete. Moving models of the BT tank in 1:5 scale were also built. The model was tested. It completely satisfies your orders given in the summer of 1934 to turn the BT tank into an even more powerful and maneuverable fighting vehicle.
The BT tank with the new drive can continue to move, maneuver, and fight, despite the heaviest of damage in battle: the loss of one or both tracks and up to four wheels out of eight. The crew retains the ability to fully fight and defeat the enemies of our socialist Motherland with only four wheels (as long as the tank retains balance), as the great Bolshevik party of Lenin and Stalin commands. In battle, every Bolshevik and conscious worker and peasant fight until the last drop of blood and die, if needed, rather than surrender to the enemy.
The new type of drive increases the mobility of the BT tank in heavy terrain (plowed soil) by 4-5 times and allows it to traverse grades of up to 25 degrees on wheels. The new design reduces the turning radius by a factor of two, from 10 to 5-6 meters, doubling the mobility of the tank.
In case the track is knocked off, the tank moves from tracked to wheeled mode automatically, without need for the crew to stop or exit the tank.
We named this new invention "BT-IS". The idea to improve the mobility of the BT tank in this direction belongs to you, comrade Stalin. Our beloved leader, a Bolshevik, the commander of the Ukrainian Military District, comrade I.Ye. Yakir told us so. Carrying out your will, comrade Stalin, in the shortest possible amount of time was our duty to the Party.
The great Party of Lenin, directed by you, the heroic Worker and Peasant Red Army, and our iron-willed People's Commissar of Defense comrade Voroshilov, raised us with discipline and will, tenacity and steadfastness to solve any problem given to us by the Party.
At the same time as we started this project, we began to design and produce a new wheel-track drive for the BT tank. It is also complete. Blueprints and 1:5 scale models are also complete. A new suspension for the wheel drive and a ball-jointed link track have been designed for it. According to our calculations, the BT tank with an ordinary M-5 engine can reach a speed of 105 kph on tracks and wheels, twice as fast as when using ordinary tracks (51.6 kph). The tank can turn 360 degrees in place with the new tracks. The tracks are rubber, and the vehicle moves silently. The vehicle can be used tactically due to its all-terrain mobility at high speed and silent movement.
In both of our designs, we aimed for minimal changes to BT-2 and BT-5 designs and reached this goal. This allows new drives to be installed on existing types of BT tanks with few changes and introduce the drive into production easily.
The invention of both types of drives belongs to a young Bolshevik and commander of the 4th Tank Regiment of the Ukrainian Military District, N.F. Tsyganov, a talented self-taught designer and inventor. In 1934, Tsyganov was awarded a gold watch by People's Commissar of Defense comrade Voroshilov and promoted from junior commander to commander for the invention of an automatically engaging towing hook for the BT, T-26, and T-27, which was accepted into service with the RKKA. We were only assistants in his realization of his inventions.
During 4 months of work, our group under the direction of comrade Tsyganov and supervised directly by the commander comrade Yakir, working 16-18 hours per day, created over 500 blueprints and about 3000 parts for the models of the vehicles. Today, we are happy to report to you that work on both types of drive are complete.
We await your directions and further instructions.
Work on these projects deepened our knowledge and only renewed our energy. We are not tired, if anything, we are stronger, tougher, and ready for new, more strenuous work.
All workers of the USSR see the gathering clouds of a new war, watching how German and Japanese fascists madly prepare for an invastion of the USSR. As all workers and peasants of the USSR, all soldiers, commanders, and political workers of the Worker and Peasant Red Army, we burn with the desire to give our knowledge and strength, will and energy, all our blood drop by drop, as you teach us, comrade Stalin, to the mission of securing the defenses of our great Motherland, the Fatherland of the Proletariat of all nations, the building of socialism and communism in our country, and the international proletarian revolution.
Kiev, April 23rd, 1935."