V-2 rocket offensive began on 8 September 1944, when "Lehr- und Versuchsbatterie No. 444" () launched a single rocket guided by a radio beam directed at Paris. Wreckage of combat V-2s occasionally contained the transponder for velocity and fuel cutoff. The painting of the operational V-2s was mostly a ragged-edged pattern with several variations, but at the end of the war a plain olive green rocket also appeared. During tests, the rocket was painted in a characteristic black-and-white chessboard pattern, which aided in determining if the rocket was spinning around its longitudinal axis. The original German designation of the rocket was "V2",
Type 4 Ha-To m (1.9 mi) and launched a 170 kg (374 lb) projectile. The gun itself weighed close to 1.5 tons, and to keep the center of gravity from shifting and tipping the vehicle over, it could not be elevated more than 50 degrees. The first prototype was completed in late 1944 and taken to the Imperial Japanese Army Academy for testing. Although testing indicated that it would be an effective weapon, it was expensive to produce, and the Japanese Army Technical Bureau shifted its attention to self-propelled multiple rocket launchers instead. An additional three units were produced before the surrender of