<Li> Henryk Magnuski, a Polish engineer working for Motorola, co-designed the SCR - 300 radio in 1940 . It was the first small radio receiver / transmitter to have manually set frequencies . It was used extensively by the American Army and was nicknamed the walkie - talkie . </Li> <P> Polish engineers who escaped German occupied Poland contributed to weapon developments during the war . A Polish / Czech / British team brought the 20 mm Polsten to fruition as a simpler and cheaper to produce but as effective derivative of the 20 mm Oerlikon gun . </P> <P> The Polish Home Army was probably the only World War II resistance movement to manufacture large quantities of weaponry and munitions . In addition to production of pre-war designs they developed and produced during the war the Błyskawica submachine gun, Bechowiec, KIS and Polski Sten machine pistols as well as the filipinka and sidolówka hand grenades . During the Warsaw Uprising Polish engineers built several armoured cars, such as the Kubuś, which also took part in the fighting . The KIS was designed and made in the Jan Piwnik's "Ponury" ("Grim") guerrilla unit that was operating in Holy Cross Mountains region . It was probably the only kind of modern firearm that could be manufactured in the forest without the need for sophisticated tools and factory equipment during the Second World War . </P>

The nation that experienced the greatest losses in world war ii was