As Germany learned very painfully during World War II, no super-power can be a global super-power, without a large, powerful navy.
For fighting a World War II style conflict, there is only one perfect navy, the US Navy. Not only because of the advanced warships built, but also because of the fleet supply train developed during the war, and the refinement of amphibious assault warfare.
The Washington Naval Treaties between the World Wars limited German, Japanese, and Italian naval ambitions, but also hurt Britain and America. A moratorium on capital ships was imposed until 1931. All of the major powers, began designing new capital ships as soon as it expired.
Japan eventually produced the Yamato Class super-battleships, Italy concentrated on new designs of light, fast, heavily armed battleships and cruisers. Germany, as outlined in Lack & misuse of naval power by the Axis, chose to rebuild land forces first, and only produced prototypes of advanced warships.
Britain, like America went to work on new modern design warships. However, a number of economic and political issues of the 1930’s, as well as standing alone against Hitler’s U-boat assault from 1940-42, conspired together to severely delay British capital ship development.
That being said however, the US Navy as it existed by VJ Day 1945, owes much to the Royal Navy.
Britain invented the aircraft carrier. But furthermore, Britain pioneered the concept of the aircraft carrier as an offensive naval asset unto itself, with the 1918 Tondern Raid by 7 biplanes launched from HMS Furious. The first ever, carrier-strike.
Without Britain’s ingenious dreadnought battleship layout and design, America’s advanced Iowa Class battleships might not have existed, as we know them today. HMS Dreadnought‘s main armament being lined up coaxial to the keel, was as revolutionary to naval gunnery as the internet to communication.
Britain being an empire with global naval outposts, sparked the idea of the US Navy fleet supply train of forward Pacific bases in World War II, combined with replenishment at sea (RAS). The Royal Navy had begun experimenting with RAS as early as 1870. RAS enabled US carrier task forces to remain at sea, far longer than if they had to return to base to refuel and provision.
The Royal Navy’s bad experiences at Gallipoli in World War I, motivated the US Navy and Marine Corps to develop solutions for amphibious warfare during military interventions in Central America. By December 1941, the foundation had already been laid for the specialized amphibious warfare and associated assault craft which breached Japan’s island chain fortress strategy so quickly, as well as Hitler’s Atlantic Wall.
Wartime convoys to both protect merchant and troops ships, as well as lure enemy submarines to their destruction, was another British innovation. Convoys not only saved Britain in World War II, but ensured the Allies were ready by D-Day in 1944.
Britain further innovated the convoy system with the addition of escort aircraft carriers, at first only carrying fighters to shoot down German Condor long-range naval bombers. But, eventually carrying bomber/torpedo planes to help sink U-boats with torpedoes, bombs and depth charges.
The US Navy, adapted the escort carrier in the Pacific, to provide extra fighter cover for large carriers, to hunt for submarines, and to provide air support to landing forces; keeping fleet carriers free for naval combat.
The US Marine Corps, though very much its own service by World War II, was the land component of the US Navy. It was outfitted with all of the same basic equipment and weapons of the US Army.
The US Marine Corps existence, owes much to Britain’s Royal Marines, having been founded in 1755, a full two decades before the founding of America’s Continental Marines. Both organizations, are among the few in the world, specifically trained in naval amphibious warfare.
So, while the perfect navy to fight a World War II style conflict, would be the US Navy, its ships, aircraft, equipment and operations doctrines; the ideas sparking it’s creation, are largely that of the Royal Navy.