The Yak-9 and its variants were the final development of a line of propeller driven Russian fighters that started with the Yak-1. It was the mainstay of the Soviet Air Force in the middle and late years of WWII and was produced in greater numbers than any other Soviet fighters. By the middle of 1944 there were more Yak-9s in service than all other Soviet fighters combined. Production of the Yak-9 continued into 1947 and a staggering total of 16,769 were built.

Like other Russian fighters, it was designed for mass production and durability. It had little in new technology and due to chronic Soviet shortages of strategic materials, it used the absolute minimum of them, instead using wood and plywood. The idea of the Soviet High Command was - knowing they could not build superior fighters in any number due to shortages - they would rely instead on numerical superiority rather than technical superiority. Nevertheless, it could be a formidable fighter, particularly at low altitude and when the Soviet pilots had numerical superiority over the Luftwaffe fighters opposing them. Fortunately for the Soviets, this was a common scenario on the Eastern Front.

The Yak-9 was not a great fighter one-on-one in the air superiority role, but it did have one saving grace in its favor. It had an excellent tight turning diameter at low speeds, which allowed it to turn inside of the German fighters it faced. This meant that the Yak-9 could usually get inside of an opponent in a sustained turn. Which in turn meant it could avoid getting shot down by going into a tight turn, but did not necessarily mean improving its chances of shooting down its opponent. The Luftwaffe pilots - seeing they were being outmaneuvered in the turn, would simply break off and try again from another angle.

By all reports the Yak-9 was a durable fighter, capable of absorbing a lot of battle damage and still making it home. It was also a successful ground attack fighter and some variants were specialized for that role. On the debit side, compared to most of its contemporaries, the Yak-9 was relatively slow, had a slow rate of climb and performed badly at high altitude. It was basically a short-range low-altitude fighter and not particularly well armed.

The Yak-9 first made its presence felt during the Battle of Stalingrad in early 1942. The first production Yak-9s had wooden wings with metal spars and a mixed construction fuselage with a molded plywood skin. Power came from a liquid cooled "Vee" engine, the M-105PF, rated at approximately 1,100 hp. Armament consisted of one 20mm cannon firing through the center of the propeller boss and one 12.7mm (.50 caliber) machine gun firing through the engine cowling. The Yak-9 could also carry six rockets or two 220-pound bombs.

The Yak-9D, introduced in the summer of 1943, was a longer-range escort fighter version carrying additional fuel in two outer wing panel tanks and an optional tank under the cockpit. (Soviet pilots must have viewed the latter as a mixed blessing.) The Yak-9D was powered by a 1,360 hp. M-105PF-3 engine. Specifications for the Yak-9D are as follows (from The Complete Book of Fighters by Roy Cross): Max speed 374 mph at 10,170 ft., 332 mph at sea level; Climb to 16,405 ft. in 6 minutes; Max range 870 miles; Empty weight 6,107 lbs.; Max loaded weight 6,790 lbs.; Span 31 ft. 11.5 in.; Length 28 ft. .75 in.; Height 9 ft. 10 in.; Wing area 184.6 sq. ft.

The Yak-9DD was an even longer-range version (up to 1,367 miles). It was used to escort U.S. heavy bombers on shuttle missions against the Romanian oil fields and also over Italy and Yugoslavia.

Later in 1943 came the limited production Yak-9K, which featured a 45mm cannon.

The 9M variant began production in late 1943. This standard version was armed with one 20mm cannon and two .50 cal. machine guns, all concentrated in the nose of the airplane. The wingspan was reduced and the ribs were made of lightweight duralumin. The engine was upgraded to the 1,240 hp. M-105PF-3. The Yak-9MPVO was a night fighter variant equipped with a searchlight and a radio.

The Yak-9PD was an interesting experimental high altitude variant. It had an M-105PD engine with a two-stage supercharger. The armament was reduced to just a single 20mm cannon, firing through the propeller boss, to reduce weight. It may have been deployed in very limited numbers against high-flying German reconnaissance airplanes late in the war.

The Yak-9P version appeared after the end of hostilities in 1946 and featured an increased armament with one or two fuselage mounted 20mm cannon synchronized to fire through the propeller arc, in addition to the usual cannon mounted in the propeller boss. China received Yak-9P fighters from the USSR after the Communist take-over and supplied some to North Korea, where they were used against UN forces at the beginning of the Korean War. Some were shot down by American P-51s.

The Yak-9 entered service in October 1942 and subsequent versions remained in service with the Soviet Air Force and later its client states (including Poland, Hungary, China, Yugoslavia and Bulgaria), into the early 1950s.