Błyskawica was the backbone of the Polish underground weapons industry, along with the Polish version of the Sten submachine gun. Originally produced in Britain, the Błyskawica was covertly manufactured in mass numbers. It was designed by two Polish engineers, Wacław Zawrotny and Seweryn Wielanier, and it combined the exterior of a German MP-40 sub-machine gun and the interior mechanism of the British Sten. All parts of the weapon were joined with screws and threads, rather than bolts and welding.