Before dawn, German, Hungarian, and Italian forces invaded Yugoslavia from Austria, Romania, Bulgaria, and Albania. German Luftwaffe swiftly destroyed Yugoslavian Air Force on the ground and devastated Belgrade with aerial bombing between 0700 and 0830 hours, killing 4,000 civilians; on the ground, German forces spearheaded by armor reached the Skopje and Veles areas in southern Yugoslavia. On the same day, German, Hungarian, and Italian forces invaded Greece from Bulgaria. Unlike the success in Yugoslavia, the invasion was slowed by Greek and British troops at the Metaxas Line. After sundown, a Luftwaffe raid on Piraeus, Greece got an unexpected boost when the ammunition ship Clan Fraser was hit, with the resulting blast doing more damage to the port facilities than the aerial bombs dropped by the Germans; the explosion also caused the sinking of 11 other freighters
