After the fall of Germany in May of 1945, the Soviet Union (as well as the Allies) was privy to pieces of captured data regarding turbojet engine technology. The age of the jet would soon be upon the world with all of the victorious world powers benefitting from the work that had been done by the German engineers in the months and years leading up to the end of World War 2. Not only was valuable data captured by the victors but, as in the case of the Soviet Air Force, large stores of engines were netted in abandoned or conquered German-run production facilities. Such technology could then be thoroughly tested and, ultimately, reverse-engineered to garner new insight into the evolving technology of the time. The German Junkers Jumo 004B series turbojet engine became one such spoil of war for the Soviet Union and it was quickly collected in quantity and delivered for review to various Soviet firms.
The Soviet Union, along with the British and the Americans, had persevered to bring about their own indigenous jet engine programs during the war with the British proving ahead of the curve by war's end (next to Germany). As such, Soviet leader Joseph Stalin encouraged the use of the captured German engines to facilitate introduction of new Soviet jet-powered fighters until proven homegrown technology could become available in quantity.
Engineers received German engine examples and took to fitting the powerplant in to a highly-modified airframe consisting of Yak-3 piston-powered fighter that had served in the war prior - now available in some numbers. The end result would create a light airframe that meshed well with the relatively underpowered performance inherent in the Jumo 004B. The Yak-3 was a conventional fighter aircraft in most respects, fielding low-set monoplane wings mounted ahead of amidships, a single-seat cockpit with adequate views all-around and a forward-mounted engine compartment. The empennage was traditional, sporting a short vertical fin with horizontal tailplanes. In the revised design, the piston-powered engine was replaced by the turbojet (now known under the Soviet designation of "RD-10" and constructed by Tumansky) at the front of the design. Gone was the three-bladed propeller as well, this replaced by the gaping air intake required to aspirate the engine. The low-set monoplane wings remained as did the aft-end of the fuselage and tail-dragging undercarriage of the original aircraft to help speed up development. The aircraft achieved first flight on April 24, 1946 and was designated as the "Yakovlev Yak-15" - becoming one of the earliest jet fighters available to serve with Soviet Air Force. The aircraft was publically displayed in her full aerial glory during the upcoming Tushino Aviation Day of August, 1946.
After a period of evaluation ending in 1947, to which the aircraft showcased itself quite well under the control of Soviet test pilots, the type was accepted into military service and formally armed with a pair cannons - initially 2 x 20mm BM-20 series and then 2 x 23mm Nudelman-Suranov NS-23 series cannons - these fitted to the upper forward nose assembly. Each cannon was afforded 60 projectiles of ammunition. Power from the RD-10 engine provided for a top speed of up to 500 miles per hour at altitude with a range of 315 miles. The aircraft's service ceiling topped off in the vicinity of 43,800 feet. Deliveries of the new Yak-15 occurred in 1947 and production outputted a total of at least 280 examples from 1946 to 1947. NATO went on to codename the new fighter as "Feather" in keeping with tradition (Soviet fighters were given "F" names while bombers were given "B" names).
The Yak-15 was evolved into a two-seat trainer as the "Yak-21". This airframe featured seating for an instructor and student pilot (in a forward cockpit, lengthening the fuselage as a result) as well as redundant flight controls in both seating emplacements. Training was required for all pilots as jet-powered flight brought about a whole new set of rules and concerns for "green" and veteran Soviet airmen alike. The Yak-15U was a developmental model fitting powered tricycle landing gear but was not produced en mass. The Yak-15U existed in a two-seat trainer mount under the designation of Yak-21T but, again, these did not enter serial production with the Yak-15 line.
The Soviet Air Force would become the only operator of the Yak-15 for its tenure was relatively short-lived and production was never truly quantitative enough to see export to allies. The Yak-15 was retired from service by 1953, quickly replaced by improved jet-powered types including the revolutionary MiG-15 of the Korean War.