After World War II, Western engineers drew inspiration from the German Sturmgewehr 44 assault rifle, which offered a compromise between bolt-action rifles and submachine guns. Among them was Kazimierz Januszewski (also known as Stefan Janson), a Polish engineer who had worked at the Polish national arsenal during the 1930s. After being mobilized during World War II he escaped German and Soviet forces and made his way to England, where he was a part of the "Polish design team" at Enfield Lock's Royal Small Arms Factory. The factory was run by lieutenant colonel Edward Kent-Lemon. As Januszewski was developing a new rifle, the "Ideal Calibre Board" was searching for a replacement for the .303 cartridge. The Board decided on an optimal 7 mm cartridge on which Januszewski and the two teams working at Enfield had to base their designs. One design team led by Stanley Thorpe produced a gas-powered rifle with a locking system based on the Sturmgewehr. The design used steel pressings which were difficult to obtain, and the design was scrapped. The result of the Polish design team's efforts was the EM-2, which broke significant new ground. The EM-2 contained some similarities to the Soviet AK-47, although Januszewski had never seen the Soviet rifle. The first significant bullpup assault rifle came from the British programme to replace the service pistols, sub-machine guns, and rifles. In the two forms of the EM-1 and the EM-2, the new rifle concept was born as a result of the experience with small arms that was gained during the Second World War. It was obvious that the modern warfare would require the infantry to be armed with a light, selective fire weapon, with effective range of fire much longer than that of a submachine gun, but shorter than that of conventional semi-automatic or bolt action rifles. The bullpup design was seen as a necessity to retain the accuracy at range while reducing overall length. The EM-2 was adopted by the UK in 1951 as the world's first (limited) service bullpup rifle, but was promptly displaced by the adoption of the 7.62×51mm NATO (0.308 in) cartridge, to which the EM-2 was not easily adapted. The decision was rescinded and a variant of the more conventional FN FAL was adopted in its place. A 7.62×39mm M43 calibre experimental assault rifle was developed by German A. Korobov in the Soviet Union around 1945, and a further development, the TKB-408 was entered for the 1946–47 assault rifle trials by the Soviet Army, although it was rejected in favour of the more conventional AK-47.