In December 1941, while German troops advancing towards Moscow and Leningrad, Tito formed the First Proletarian Brigade – the first regular unit of the National Liberation Army, in Rudo, a small village in Bosnia. The Igman march was one of its first major trials. Near the end of January 1942, the brigade found itself on the mountain Romanija, surrounded by strong German forces. The brigade staff decided to execute a risky, but the only possible move: to pass right by Sarajevo, then over the Igman Mountain, and towards the liberated town of Foca, where the Supreme headquarters with Tito had already managed to break through. The march took place in the night between January 27 and 28, 1942, under conditions of extreme cold (up to –40C°) and deep snow. The Igman march has become a legend because the fighters withstood this terrible cold from which even trees cracked.