From World War II at Sea, by Craig L. Symonds (Oxford U. Press, 2018), Kindle pp. 101-102:
German intervention in the Greek war was decisive. Within days, British and Greek ground forces were in full retreat. If the Germans had failed to provide adequate air cover for Iachino’s fleet, their aircraft proved devastatingly effective in the land war, and Stuka dive-bombers and Junkers level bombers dominated the skies. In a kind of mini Dunkirk, British transports and destroyers sought to rescue the hard-pressed Allied forces. More than fifty thousand men were successfully evacuated from mainland Greece and carried 250 miles southward to the island of Crete, though four thousand British soldiers and two thousand colonial troops from British Palestine had to be left behind to become prisoners of war.
Cunningham issued orders that “no enemy forces must reach Crete by sea.” Nor did they. Absent a surface navy, the Germans could not pursue their foes across the Aegean. But on May 20, thirteen thousand German paratroopers jumped onto the island from the air. The paratroopers suffered horrific casualties, and initially the British and Greek commanders believed they could contain them. But poor Allied coordination allowed the Germans to secure the airfields, and that enabled them to fly in transport planes filled with reinforcements and supplies. Within days, the Allies had to evacuate Crete as well.
As at Dunkirk the year before, every available destroyer was assigned to the task, and as at Dunkirk, the evacuation had to take place at night due to German control of the skies. For four consecutive nights, from May 28 to June 1, the destroyers crept in at midnight and loaded troops from the jetties, putting to sea well before dawn filled with exhausted and hungry soldiers. Some 16,500 men were evacuated, though once again more than 5,000 had to be left behind. The Luftwaffe pursued and attacked the Allied ships all the way across the Mediterranean, and the toll on Cunningham’s fleet was shocking—greater than Italian losses in the Battle of Cape Matapan. Altogether the British lost three light cruisers and six destroyers sunk and sixteen more ships severely damaged, including the battleships Warspite and Barham, as well as the new carrier Formidable. More than 2,400 British sailors lost their lives.
Despite efforts by the Regia Marina, the British still commanded the sea, but the Germans controlled the air, so—much like the Italians—the Royal Navy could not operate effectively beyond the umbrella of land-based air cover. Arthur Tedder, head of the Royal Air Force, observed that “any excursion [by warships] outside a radius of about 150 miles to the east and north of Alex[andria] is an expensive adventure.” The Royal Navy retained its presence in the eastern Mediterranean, but its reach had been severely limited.