Narodowe Siły Zbrojne (English National Armed Forces, NSZ) was a Polish anti-Nazi and later anti-Soviet military organization which was part of the Polish resistance movement in World War II. The NSZ fought the Nazi Germany and Soviet forces, regarding them as occupiers and enemies of independent Poland. The NSZ was also engaged in fighting Soviet-allied Polish communist partisan forces, such as Gwardia Ludowa and Armia Ludowa. The NSZ was the third largest Polish resistance movement of World War II, after the Home Army and Bataliony Chłopskie. The number of its soldiers ranged from 70,000 to 75,000.
The NSZ was created on September 20, 1942, as a result of the merger of the Military Organization Lizard Union (Organizacja Wojskowa Związek Jaszczurczy) and part of the National Military Organization (Narodowa Organizacja Wojskowa). At its maximum strength in 1943-44 the NSZ reached between 70,000 and 75,000 members, making it the third largest organization of the Polish resistance (after the Home Army (AK) and the Bataliony Chlopskie). NSZ units participated in the Warsaw Uprising.
In March 1944 the NSZ split, with the more moderate faction coming under the command of the AK. The other part of the organization became known as the NSZ-ZJ (the Lizard Union). This branch of the NSZ conducted operations against Polish communist activists, partisans and secret police, the Soviet partisans, NKVD and SMERSH, and their own (NSZ) former leaders. The actions claimed hundreds of victims, including many Jews.