from naval history.net
Yugoslavia and Greece - Germany invaded both countries on the 6th April. By the 12th April , they entered Belgrade and within another five days the Yugoslav Army had surrendered. Greek forces in Albania and Greece suffered the same fate. Starting on the 24th April over a period of five days, 50,000 British, Australian and New Zealand troops were evacuated to Crete and Egypt in Operation ‘Demon’. The Germans occupied Athens on the 27th.
North Africa - Germans entered Benghazi on the 4th April and by mid-month had surrounded Tobruk and reached the Egyptian border. Attacks on the British and Australian troops defending Tobruk were unsuccessful, and an eight-month siege began.
16th April - Action of Sfax, Tunisia - Capt P. J. Mack with destroyers HMS Janus, HMS Jervis , HMS Mohawk and HMS Nubian sailing from Malta intercepted a German Afrika Korps convoy of five transports escorted by three Italian destroyers off Kerkennah Islands, east of Tunisia. All Axis ships were sunk including the destroyers “BALENO” (foundered next day), “LAMPO” (later salvaged) and “TARIGO”. In the fighting HMS Mohawk was torpedoed by “Tarigo” and had to be scuttled.
Malta - In the first week of April, the aircraft carrier HMS Ark Royal escorted by Force H sailed from Gibraltar and flew off 12 Hurricanes for Malta. Three weeks later the operation was repeated with 20 more aircraft. From the other end of the Mediterranean, Alexandria-based battleships HMS Barham, HMS Valiant and HMS Warspite together with carrier HMS Formidable covered the movement of fast transport HMS Breconshire to Malta. On the 21st they bombarded Tripoli on their return.
27th April - As units of the Mediterranean Fleet carry out the Greek evacuation, destroyers HMS DIAMOND and HMS WRYNECK rescued troops from the bombed transport “Slamat”, but were then sunk by more German bombers off Cape Malea at the southeast tip of Greece. There were few survivors from the three ships.