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 US F6F Hellcat (which achieved kill ratios of between 13 to 1 and 19 to 1 against Japanese "Zero" fighters) or P-51 Mustang.