From the Wikipedia page 
Due to a lack of jobs, declining quality of life, and the failure of the Hungarian economy, an uprising occurred on October 24, 1956. The Corvin Passage was immediately recognized by the rebels as a strategic location due to its importance as a traffic junction, and its great symbolic value (mainly from its location near the Kilian barracks and Radio Budapest). The Passage provided a good defense point, with narrow streets that limited the movement of larger vehicles, such as tanks and trucks.
László Iván Kovács is said to have first fought at the Corvin Passage in October during the early stages of the Hungarian Revolution (1956). He first began demonstrating outside of a radio station and later that day used a gun on Üllői Avenue to fight against Soviet tanks. On October 26, he joined other armed revolutionaries in Corvin where he eventually became the leader of a unit of 1,000. It was here that he set up his base in Corvin's resident cinema where his successor, Gergely, also set up command.
The soldiers at Corvin had already resisted a Soviet offensive on October 24 and the Soviets were later defeated, suffering heavy casualties. The strategy then was to gather intelligence and attack with a renewed offensive on October 28. To battle this offensive, the Soviets appointed the leader of the 33rd Mechanized Infantry Division, Gennady Ivanovich Obaturov. Heavy artillery support, poor intelligence and insufficient planning resulted in the failure of the offensive. On October 29, László negotiated a cease fire resulting in a Soviet withdrawal from October 29 to October 31. Despite his successes as a commander, after November 1 László was deposed for unknown reasons and replaced with Gergely.
Nicknamed 'Bajusz' for his 'Twirly' mustache, Gergely Pongrátz fought in less harmonious circumstances than his predecessor. Though he commanded 4,000 militia compared to László's 1,000 militia, he still had to contend with a second Soviet intervention which had turned back toward the city after it had withdrawn and attacked on November 5. His soldiers fought from the windows of buildings, destroying Soviet tanks with makeshift Molotovs. With these tactics, Gergely gained a degree of success destroying a reported 12 tanks. However, under heavy Soviet artillery and mortar fire, the defense of the passage became steadily more difficult, and with the desertion of 300 troops on November 6, defensive capabilities were damaged and made fighting against the Soviets solely guerrilla. Then on November 9, Gergely's forces were defeated and he fled to Austria, ending the battle