The Regia Marina was, without a doubt, the most effective branch of the Italian military in the Second World War. For three years, the battleships and heavy cruisers of the Italian fleet denied the British use of the Mediterranean for sending reinforcements abroad. Additionally, Italian submarines played an oft-overlooked part in the Battle of the Atlantic. Torpedo Boats, Explosive Motorboats, and frogmen of the MAS units managed to cripple battleships. However, a lack of radar, aircraft carriers, and increasingly severe fuel constraints hampered their operations throughout the war. In spite of these disadvantages, the Regia Marina waged a seesawing war with the famed Royal Navy for control of the Mediterranean. Each side gained the advantage for a time, only to lose it again until the collapse of the Italian position in 1943.