Naval combat underwent a significant metamorphosis during World War II. Nazi Germany and Imperial Japan launched some of the most powerful battleships ever to sail the world's oceans, yet the conflict witnessed the emergence and triumph of the aircraft carrier as the 20th century's true monarch of the seas. Submarine warfare expanded and developed, while aircraft technology and doctrine experienced several revolutionary changes due to the unforgiving demands of the new combat environment.

Popular accounts of World War II frequently focus on the dominance of German panzers over the more lightly armored, lightly armed tanks of the Soviets, British, and Americans, or the superb fighting skills of the Waffen SS and ordinary Wehrmacht soldiers. Germany's land forces enjoyed an undoubted advantage over their enemies thanks to excellent vehicle technology, while German soldiers slaughtered vast numbers of Soviet conscripts and proved formidable opponents even to their better-trained English and American counterparts.

However, the Axis failed to secure either the seas or the skies, and their defeat in these theaters ultimately led to their doom. Many highly advanced aircraft designs languished on the drawing boards of Junkers and Messerschmitt engineers, left undeveloped due to high command disinterest or simple lack of resources. The most advanced fighters developed by Nazi Germany and Imperial Japan were equaled or outmatched by such aircraft as the U.S. F6F Hellcat (which achieved kill ratios of between 13 to one and 19 to one against Japanese “Zero” fighters) or P-51 Mustang.

America, with its vast productive resources and immense manufacturing capacity, single-handedly supplied the materiel that saved Britain and the Soviet Union from defeat. It did so by controlling the sea lanes and eventually ending much of the threat of U-boat attack, supplying England and Russia with staggering quantities of food, weapons, raw materials, trucks, tanks, aircraft, prefabricated buildings, boots, ammunition, medicines, and even entire locomotives and sets of railway rolling stock. Over 50 percent of the Soviet Union's entire wartime supply base, from food and clothing to weapons and vehicles, came directly from the United States.

In time, the Allied navies progressively destroyed their Axis counterparts, ensuring clear sea lanes, high strategic mobility for seaborne invasions, and large-scale air support that eventually battered the Axis armies into submission. Just as the Luftwaffe paralyzed Poland's defenders in 1939 with air superiority, the Allies' mastery of naval and aerial warfare turned the tables to paralyze the Axis.

While many large-scale naval engagements were fought in the Pacific at places like the Coral Sea, Midway, and the Philippines, engagements were rare in Europe. There were flurries of action as the German warships Admiral Graf Spee and Bismarck were hunted and destroyed in 1939 and 1941, and there was a constant battle between surface ships and German U-Boats that lasted throughout the war. But there was only one major naval engagement fought between battle fleets in Europe. At the Battle of Cape Matapan, the British Royal Navy and the Royal Australian Navy would square off with the Italian Regia Marina in early 1941.

Though it was the most decisive naval battle in the Mediterranean, the Battle of Cape Matapan has largely been forgotten today, even as military historians have recognized its significance, and some have even compared it with the legendary Battle of Trafalgar in 1805. Indeed, the battle shaped the remainder of the war in the Mediterranean, which would prove crucial when the Western Allies would use it to amphibiously invade Sicily in 1943, marking their return to the European continent.