Boats in World War II
Beyond the vast differences in submarines, the naval technologies of the different nations of World War II are generally comparablewhile of course there are infinite notable distinctions, a general understanding of boats and their purposes in the War can be understood by a basic introduction, disregarding the differences between Allied and Axis navies.
With the main role of deploying and recovering aircraft, carriers played a large role in World War II, the most notable being the Japanese attack on Pearl Harbor, where aircraft carriers were not in port and so escaped damage. A large number of the major Pacifica battles involved aircraft carriersspecifically, the Battle of Midway was an engagement in which four Japanese carriers were sunk in a surprise attack by planes from three American carriers (this is actually often considered the turning point of the war in the Pacific). Quite literally, the aircraft carrier was the Queen of the Seas in WWII. The importance of all other boats pales in comparison.
Also referred to historically as the dreadnought, the tale of the battleship in World War II is sad one. In the beginning, famous and valiant ships like Bismarck, Missouri, and the Japanese Yamato were all launched in preparation for the war. And indeed, during the Battle of the Atlantics early stages, Germany used battleships to threaten Allied convoys, and British Prime Minister Winston Churchills first major naval aim was destroying their battleships Scharnhorst and Gneisenau. within the next few years in preparation for the coming of World War II. However, the technology of the aircraft carrier quickly overtook the battleship. Aircraft with ranges of hundreds of milesand soon with radar to bootsurpassed the utility of battleships guns. By the end of the war, most of battleships were taken out of commission or simply scrapped.
HMS Valiant in Plymouth Sound, England
As with battleships, the destroyer ships history is marked by a constant need to keep up with technology. In World War I, the new presence of U-boats presented the dire need for sonar and depth charges, in order to somehow counter a novel threat; in World War II, the new technology was highly-advanced aircraft. Suddenly the primary weapon of sea power, destroyers had to quickly equip themselves with new anit-aircraft guns. Unlike the battleship, the destroyer overcame technological threats and was not vanquished into naval history.
DD-651 USS Cogswell
A cruiser is known to be a fast, long-range, lightly-armored ship. There are various classesarmored cruisers, protected cruisers, heavy and light cruisers, and the impractical cruiser-battleship hybrid the battlecruiser. The difference between cruisers usually depends upon some surface dissimilarity, like armor, size, or battery; for example, heavy cruisers usually had 8-inch guns, or 200 mm, while light cruisers had guns of 6-inches, or 150 mm. These differences resulted in vastly diverse destructive powers. Cruisers were in general used for fire support and served as fleet escorts. They were heavily used.
USS Helena, which saw heavy action in WWII, here pictured
Firing her 8 inch battery guns at a North Korean enemy in 1950.
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Perhaps one of the most interesting stories regarding boats in WWII is that of the Higgins Boat. It was used to transport troops, and was the main boat employed for the D-day invasion.
 Image source: http://www.fleetairarmarchive.net/Ships/Victorious.html
 Image source: http://www.softwhale.com/history/D-Day/FatherJoeLacy.htm