The Yak-1 is a Soviet single-engine fighter of the WWII era. It was the first combat aircraft designed by Alexander Yakovlev's construction bureau and was produced from 1940 to 1944, with a total of 8,700 aircraft built.
The Yak-1B variant was a culmination of all 1942 efforts to improve the Yak-1. Work began at TsAGI, where research into improving the water and oil radiators took place between 24th May and 10th June 1942, and work to increase the top speed was conducted between 20th and 26th July 1942. Tactical characteristics of the Yak-1 were significantly improved as a result, leading to Yakovlev's request to the Minister of Aviation to mass-produce a test batch of 20 improved aircraft for combat testing at the front.
However the improvements looked so good on paper that a test batch was skipped, and a Defence Committee Directive dated 11th August 1942 ordered a new and improved Yak-1 into mass production. Improved armament triggers and a cockpit with improved rearward visibility were welcomed by Soviet pilots and became standard on all contemporary Soviet fighter planes.