When the Third Reich occupied Czechoslovakia in 1938, the Czechoslovak air force was broken up. Bulgaria used the opportunity to acquire large numbers of relatively modern ex-Czech aircraft from the Germans at a bargain price. Bulgaria purchased 78 Avia B-534 biplane fighters, 32 Avia B.71 bombers (a license version of the Soviet SB bomber), 12 Bloch MB.200 bombers, 62 Letov Š-328 reconnaissance aircraft and 28 Avia Bs.122 trainers. Deliveries of the second batch of Polish orders started in early 1939, with 33 PZL.43Bs and 8 PZL.11Fs delivered before the German invasion of Poland stopped deliveries (although two more PZL.43Bs were delivered by the Germans later). In less than 3 years the Air Force inventory had grown up to 478 aircraft of which 135 were of Bulgarian construction.