British Forces Launch Naval Attack through the Kaso Strait
Admiral Andrew Cunningham, determined that no German troop transports should reach Crete, sent Admiral King's Force C (three cruisers and four destroyers) into the Aegean through the Kaso Strait, to attack a second flotilla of transports escorted by the Italian torpedo boat Sagittario. The force sank a caïque separated from the main flotilla at 8:30 am, thus saving it from an air attack that struck the cruiser HMS Naiad at this time. The pilots were trying to avoid killing their troops in the water. King's squadron, still under constant air attack and running short of anti-aircraft ammunition, steamed on toward Milos, sighting the Sagittario at 10. King made the difficult decision not to attack, despite his overpowering advantage, due to the shortage of ammunition and a torpedo charge executed by the Italian warship. He had succeeded, however, in forcing the Germans to abort this seaborne operation. During the search and withdrawal from the area, Force C suffered heavy losses. Naiad was damaged by near misses and the cruiser HMS Carlisle was hit. Admiral Cunningham later criticized King's decisions.
Force C met up with Rear Admiral Rawling's Force A1 at the Kithera channel where more air attacks inflicted damage on both forces. A bomb struck Warspite and then the destroyer Greyhound was sunk. King sent Kandahar and Kingston to pick up survivors while the cruisers Gloucester and Fiji provided anti-aircraft support, forgetting their ammunition shortage. Gloucester was hit by several bombs while the fleet was withdrawing and had to be left behind due to the intense air attacks. Seven hundred and twenty-two officers and ratings from this ship lost their lives.
The air attacks on Force A1 and Force C continued. Two bombs hit the battleship Valiant (with Lieutenant Prince Philip of Greece on board) and later another hit Fiji, disabling it. A Junkers 88 flown by Lieutenant Gerhard Brenner dropped three bombs on Fiji, sinking it. Five hundred survivors were rescued by Kandahar and Kingston the next morning. The Royal Navy lost two cruisers and a destroyer sunk, but had managed to force the invasion fleet to turn around. In total, Royal Navy AA gunners shot down 10 Luftwaffe aircraft and damaged 16 more, some of which crashed landed upon return to base, on May 21 and May 22.
At 09:00 the waters north of Crete were cleared of enemy ships and the convoy was ordered to continue its voyage in the direction of Maleme. During the day German dive bombers based on Skarpanto and Italian planes flying from Rhodes scored several hits on British ships returning to Crete waters, thereby preventing them from intercepting the Axis convoy. The German troops on the island were anxiously awaiting the arrival of artillery, antitank guns, and supplies, but poor weather conditions so delayed the convoy that it could not reach the island before darkness. When it finally came around Cape Spatha at 23:00, a British naval task force suddenly confronted the convoy, which was on the way to Souda Bay to land reinforcements and supplies.