On this day, the southeastern European nation of Bulgaria joins the Axis powers by signing the Tripartite Pact. When the Second World War broke out, Bulgaria declared its neutrality. But Bulgaria’s King Boris was eager to expand his country’s borders, and Germany had already coerced Romania to restore south Dobruja–which had been lost in World War I–to Bulgaria. Bulgaria had chosen the wrong side in World War I, deciding that its territorial needs then would best be met by joining the Central Powers (Austria-Hungary and the German Empire). They were wrong, and King Boris was determined not to make the same mistake again. Believing Hitler’s boasts that he had already won the war, King Boris chose to pitch his country’s tent on the Axis side of the war. Hitler needed a compliant Bulgaria through which to march his troops en route to offensives against both Yugoslavia and Greece. If the Germans were victorious in Greece, Bulgaria hoped, as a new war partner, to gain access itself to the Aegean by claiming Greek territory to its south. On March 1, the Germans came marching through the Balkans, as the Bulgarian king signed the Tripartite Pact in Vienna with Hitler looking on. Bulgaria benefited in the short term from the alliance; it made territorial gains in both Greece and Yugoslavia. But Hitler was not through exploiting its “partner”-the Fuhrer wanted Bulgaria’s help in its war with the Soviet Union. While King Boris prepared Bulgarian troops for the Eastern Front in 1943, communists and agrarian reformers mounted a vigorous resistance campaign, assassinating more than 100 pro-Nazi officials. King Boris also died at this time-from a heart attack. A Regency Council was formed, which remained loyal to Germany. Successive governments rose and fell until the Soviet Union’s invasion of Bulgaria in September 1944 resulted in an armistice and a postwar, pro-Soviet Bulgaria.