In mid-1940, Italy began a period of harassment that included air attacks on Greek ships at sea and the sinking on 15 August 1940 of the anchored minelayer Helle by the Italian submarine Delfino. Once Italy declared war on Greece on 28 October 1940, the RHN was active in supporting the army and in conducting destroyer sweeps in the Ionian Sea. The RHN experienced severe losses from air attacks following the April 1941 German invasion of Greece. The surviving Greek ships, their bases seized by Germans troops, withdrew first to Crete and then to Egypt, where they were integrated into the British Royal Navy.
The Royal Navy had operational control of the Greek ships, and the RHN was responsible for their administration. The Greek ships were in need of refit and modernization, and they received from the British Navy modern fire-control systems and antiaircraft and antisubmarine armaments. The British also transferred to the RHN a variety of destroyers, corvettes, submarines, and smaller craft, including minesweepers.
RHN ships then served throughout the eastern Mediterranean. Beginning in 1942, the RHN experienced nearly continual political unrest concerning the composition of the Greek government in exile. This culminated in the April 1944 mutiny of virtually the entire RHN at Alexandria and Port Said. Although the mutiny was crushed, the Greek ships were out of action for about four months while units were purged of mutineers.
After the German retreat from the Balkans, in October 1944 the RHN returned to Greek waters. It spent the remainder of the war reestablishing itself in its home territory, opening ports, engaging communist groups that resisted the return of the government from Egypt, and containing German garrisons on the larger islands of the Aegean Sea.
Mark C. Jones
Jones, Mark C. "Misunderstood and Forgotten: The Greek Naval Mutiny of April 1944." Journal of Modern Greek Studies 20, no. 2 (2001): 367–397.; Païzis-Paradellis, Constantin. Hellenic Warships, 1829–2001. Athens: Society for the Study of Greek History, 2002.; Papastratis, Procopis. "A Fighting Navy in Exile: The Greek Fleet in the Mediterranean and Beyond." In Jack Sweetman, ed., New Interpretations in Naval History: Tenth Naval History Symposium, 363–373. Annapolis, MD: Naval Institute Press, 1991.