WW2 Naval Warfare

Operation Downfall, the planned Allied invasion of Japan at the end of WWII, would be classified in military nomenclature as a "campaign" involving several pitched battles between the invading Allied and defending Japanese forces. In terms of a single battle, this is a difficult question to answer, as the operation itself never took place. However, by analyzing both US and Japanese plans for attacking/defending the home islands, we can get a fairly good idea of how the campaign would have played out.

The first phase of "Downfall," Operation Olympic, targeted the southernmost Japanese Home Island of Kyushu. According to D.M. Giangreco's 2009 book "Hell to Pay: Operation Downfall and the invasion of Japan, 1946-1947," the forces assigned to the US Sixth Army, which was given the task of securing approximately one-third of that island, would have numbered roughly 766,700 in 14 divisions (with apparent provision for reinforcement by six additional divisions), while the defending Japanese 16th Area Army (Army Group/Front Equivalent) numbered about 917,000 in 15 divisions (plus an antiaircraft division) and 10 brigades, plus the Iki and Tsushima fortress units. The Japanese, if need arose, also had provision for reinforcements of up to four additional divisions from Honshu.

However, as mentioned above, 'Olympic' as a whole represents not a battle, but a campaign.

The most plausible prospect of seeing a 'record-breaking' single battle rests with the second phase of "Downfall:" Operation Coronet, the invasion of the Tokyo area at the Kanto Plain.

In order to achieve final victory over Japan, the Allies realized they needed to control Tokyo. Since the Japanese realized not only this blatant Allied objective, but also the rough US plan of invasion, they organized their forces to ensure that the 'Yankee Barbarians' would be crushed by one fell swoop on Honshu. According to Giangreco, the initial Allied invasion of Honshu during 'Coronet' would consist of the US First and Eighth Armies, organized into 28 divisions and 1,069,000 ground and air personnel, with reinforcements arriving in the form of 12 divisions of the US Tenth Army and the British "Commonwealth Corps," comprising an unknown, but presumably large, number of personnel. To defend Tokyo, the Japanese 12th Area Army could muster 22 divisions and 14 brigades of unknown numerical strength (Giangreco cites total Japanese regular troop strength in the Home islands as roughly 2,900,000. With ~900,000 already earmarked for the defense of Kyushu, it is reasonable to estimate that at least half of the remainder would be somewhat involved in the climactic struggle for the capital), plus plans for reinforcement by as many as 5 additional divisions from areas outside the Area Army's jurisdiction. Since this military operation would focus almost exclusively on the capture/defense of Tokyo, and was referred to by both sides as a coming 'decisive battle,' it could be fairly be referred to as such.

Thus, the final balance sheet in the hypothetical "Battle of Tokyo" would have looked something like this:

12th Area Army (Japan): 27 divisions and 14 brigades

vs

1st, 10th, and 8th Armies (USA/British Commonwealth): 40 divisions plus unknown smaller formations.

It is also important to note that the Japanese also had access to a large pool of civilian militia, called the Patriotic Citizens' Fighting Corps. Giangreco puts the strength of this organization at roughly 28 million(!), compared to the total Japanese population of ~73,000,000. This is in addition to the 1,300,000 civilians already working for the IJN and 2,250,000 working for the IJA. Such huge numbers of militia and paramilitary personnel would ensure that any large-scale confrontation would be unimaginably bloody, on top of the massive civilian casualties that would inevitably result from the fighting in the Tokyo Metropolitan Area.

Thus, it can be safely assumed that the cancelled Invasion of Japan might have produced a land battle that could be called the 'largest' and 'bloodiest' of all time, given the data we have on the opposing forces in terms of their raw numerical strength.

Four main reasons;

• She was Admiral Halsey's flag ship at the time. This meant that it was there (on Tokyo Bay)
• She was a Capital Ship, remember that there were few Capital Ships in Tokyo Bay at that time (no carriers). Most were still at sea, just in case the surrender was some sort of massive deception and the Japanese were going to attempt to surprise the sitting fleet with a massive kamikaze attack.
• She was a "hero" ship with 11 battle stars earned.
• She was named for the home state of the sitting President (Truman) and Truman's wife (Mary) christened her in 1944

"CASU" stands for Combat Aircraft Support Unit; the "F" stands for Forward Area.

The listing would normally be spelled out like this:

CASU(F)-13, Det. A

Read properly, it would read:

Combat Aircraft Support Unit, Forward Area 13, Detachment A, U.S. Navy

Records show that CASU(F)-13 was forward deployed in the Southwest Pacific on the islands of Pityilu and Ponamin Manus Province Papua New Guinea beginning in late 1945.

CASU also stands for "Carrier Aircraft Support Unit" - however, the "F" indicates it as a forward unit shore base, and not a shipboard unit.

Since this question was put into the World War 2 Category I will try to answer your question based on then and now.

In World War 2 the Navy lost a good deal of their Naval Fleet when the Japanese bombed Pearl Harbor, Hawaii. Of the ships that survived or repaired or built new the Navy used Destroyers, Battle Ships, Fletchers (medium sized ships that could hunt subs) aircraft carriers, tanker ships that supplied fuel for the ships, PT Boats that were about the size of the coast guard ships you see on television, escort ships to escort the aircraft carriers around the Pacific Ocean. small landing boats called Higgins Boats that could land the Marines and Army Soldiers on the islands or on the Beaches in France, Africa, Norway, Africa, LST boats that could carry Jeeps, tanks and other equipment.

They had some boats and tanks that could work as both "cars" and swimming tanks and boats. They were called Ducks. I can't remember what the tanks were called that could operate in the ocean and on land.

There were a lot more boats than that but that is the basic list of what the Navy used in World War 2. They also used many types of airplanes that took off from aircraft carriers and the landing strips on the islands.

In today's US Navy they do not have battleships because they were rendered as being "not useful anymore" because the Aircraft Carriers of today can do way more than any destroyer or battle ship could back in World War 2. We do still have destroyers though. We have many types of submarines now. We have ships that are large cargo ships we like to call "Roll On Roll Off" ships. One end of the RORO ships open up with a large ramp. They can haul tanks, Hummers, large vehicles of most types used by all the US military forces and a lot of heavy cargo.

There are fewer large tanker ships to supply fuel to ships and smaller boats for the Navy because many of our large ships and subs are nuclear power.

If you would like to see what the Navy has today you can go to their web site. On the search engines you can often find photos of ships too. Type in US Naval Ships on your search engines.

Aah, I forgot to tell you they have large guns, missiles, person weapons, bombs and other weapons on the Naval ships and planes. Today's ships have the capability of firing missiles that can be fired from the ships many miles from their target and have the missile land right on the spot they need to reach. The airplanes can do the same thing and some planes cannot be seen by the human eye or some radar scopes of the enemy.