weakness of his opponents and without waiting for his forces to fully assemble, rapidly went on the offensive. In March–April 1941, Rommel defeated the British forces facing him and forced the British and Commonwealth forces into retreat. The Australian 9th Infantry Division fell back to the fortress port of Tobruk and the remaining British and Commonwealth forces withdrew a further east to Sollum on the Libyan–Egyptian border. The Siege of Tobruk began by the main Axis force and a small German force pressed eastwards, retaking all territory lost to Operation Compass, and advanced into Egypt. By the end of April, Sollum had fallen and the important Halfaya Pass captured. Balkans In the Balkans, the Greeks had been reluctant to allow British troops into the country, because Britain could not spare enough forces to guarantee victory. They had, however, accepted aid from the RAF in their war with the Italians in Albania. As it became likely Germany would attack Greece, four British divisions were switched from North Africa to reinforce Greek Army. The advanced guards of these troops began arriving in March 1941, triggering the entry of German forces into Bulgaria, which made clear the German intent to invade Greece. In April 1941, Germans, Italians, Hungarians and Bulgarians made quick work of the Royal Yugoslav army. They captured Yugoslavia in 11 days and partitioned it among themselves and newly formed client states: The Independent State of Croatia and Nedić's Serbia. In spring 1941, Italy created a Montenegrin client state and annexed most of the Dalmatian coast as the Governorship of Dalmatia (Governatorato di Dalmazia). A complex guerrilla uprising of communist-led Partisans, commanded by Josip Broz Tito, soon broke out. A more ambivalent, predominantly Serb paramilitary movement of royalist Chetniks both fought the occupying forces and collaborated with them against the communists. The Partisans eventually gained recognition from the Allies as the sole resistance movement. With help from both the Soviets and the Western Allies, they turned into a formidable fighting force and successfully liberated the country. Beginning on 6 April, in the ensuing Battle of Greece the Germans had been temporarily held at the border by the Greeks. After moving through south-eastern Yugoslavia, the Germans had been able to turn the Allied flank, cutting off Greek units in the east of the country. Greek forces in central Macedonia were isolated from the Commonwealth forces moving up in an attempt stabilise the