On 20 May, Germany launched an invasion of Crete by airborne troops. The British Mediterranean Fleet deployed to counter any sea-borne reinforcement of the German forces, with three groups of cruisers and destroyers (Forces B, C and D) deployed to the north of Crete to intercept invasion convoys, while a force of battleships and destroyers (Force A1) provided cover in case the Italian Navy attempted to intervene. "Calcutta" was sent from Alexandria to join Force C, meeting it on 21 May. Force C came under heavy attack by German and Italian aircraft during 21 May, with the destroyer being sunk. On 22 May Force C intercepted a convoy of Caïques carrying German troops to Heraklion, escorted by the . While the convoy was forced to turn back, heavy German air attacks caused the commander of Force C, Rear-Admiral King, to break off the attack. The air attacks damaged the cruisers and before Force C rejoined the covering Force A1. Further attacks on the combined force damaged the battleships "Warspite" and "Valiant" and sank the cruisers "Gloucester" and and the destroyer . Force A1 was ordered back to Alexandria early on 23 May to restock anti-aircraft ammunition.