The Ukrainian Insurgent Army was a Ukrainian nationalist paramilitary and later partisan army that engaged in a series of guerrilla conflicts during World War II against Nazi Germany, the Soviet Union, Czechoslovakia, and both Underground and Communist Poland. The group was the military wing of the Organisation of Ukrainian Nationalists — Bandera faction (the OUN-B), originally formed in Volyn in the spring and summer of 1943. Its official date of creation is October 14, 1942, day of Intercession of the Theotokos feast. The battle flag of the UPA was a 2:3 ratio red-and-black banner. The flag continues to be a symbol of the Ukrainian nationalist movement. The colours of the flag symbolise 'Ukrainian red blood spilled on Ukrainian black earth'.