What were the pacific islands the us marines invaded in World War 2 island hopping campaign?

The first was Guadalcanal, in the Solomon Islands, on August 7, 1942. This was the first involvement by US ground troops in an offensive anywhere in the war. The US really was not ready but the case seemed urgent. The Japanese were building an airfield on Guadalcanal, and once it was completed from it they could interfere with the sealanes to Australia. Army troops were also involved in this campaign, though not at first.

The 2nd Battalion of Marine Raiders made a raid on Makin Atoll in the Gilbert Islands later that month, but this was not intended to be a permanent occupation. It may have been a mistake because it tipped the Japanese to the fact the the US was interested in the Gilbert Islands, and may have spurred their efforts to fortify the islands.

The Marines next landed on Bougainville, in the Solomons, in November 1, 1943, as part of Operation Cartwheel. Bougainville was never completely secured until the Japanese surrender. Army troop replaced the Marines there in January 1944. Another part of Operation Cartwheel had Marines landing on Cape Gloucester, on New Britain Island, in the Bismarck Archipelago, on December 26, 1943. Cape Gloucester is at the western end of the island. One of the great strongholds of the Japanese in the Pacific was at the other end of the island, at Rabaul. No effort was made to take Rabaul - this was one of the things the US was "bypassing". All that was wanted at Cape Gloucester was an area large enough to create an airfield. Nature was the greatest enemy here - more Marines were killed by falling trees in the rain-soaked jungle than by the enemy.

Later on November 20, 1943, the Marines landed at Tarawa Atoll in the Gilbert Islands, on the tiny island of Betio. This island was just big enough to hold an airfield, and is about the size of Central Park in New York City. Almost one thousand Marines died in four days securing Betio, and the 4500 Japanese defenders fought to the last man.

On June 15, 1944, only nine days after the Normandy landings in France, the US mounted another huge amphibious invasion in the Mariana Islands, landing US Marines and Army troops on Saipan. There was also fighting on Tinian (from which the nuclear raids were later launched) and Guam in the Marianas.

Also in June 1944 Marines landed on Kwajalein in the Marshall Islands.

On September 15, 1944, Marines landed on Peleliu, one of the least known campaigns of the war, and an island no one had heard of until the season of "Survivor" a few years ago. This was a very rough one, and probably unnecessary. The island had been included in planning as securing the southern flank of a US invasion of the southern Philippines. However, carrier raids on the Philippines revealed the Japanese were weaker than feared or expected, and so the southern Philippines were bypassed and the US proceeded directly to invade the northern Philippine Islands of Luzon and Leyte. (There were no Marines in the Philippines, or in New Guinea). No one thought of canceling the Peleliu landings though.

Iwo Jima, like Tarawa, was an all-Marine operation, lasting for six weeks beginning in mid February 1945. By this time in the war there were six divisions of Marines, all infantry. Three of them were on Iwo Jima.

The other three Marine Division, along with several US Army divisions, landed on Okinawa on April 1, 1945. Okinawa was the only island outside the Philippines large enough that the US deployed and entire field army in its capture. It sits some three hundred miles south of Japan but was considered part of the Home Islands. Its in the Tokyo Prefecture and was the prewar home of the Japanese artillery school. Japanese artillerists knew every wrinkle of the land and its status as part of the Home Islands contributed to its fanatical defense.

The terrific cost to take Iwo Jima, Okinawa, Peleliu and Tarawa, and every other island wrested at great cost from the Japanese was a large factor in the decision to employ the atomic bombs. Most of these islands were nowhere near as large as any of the Home Islands and had only some thousands of troops. In the Home Islands the civilians, including women, were being armed and trained to sell their lives as dearly as possible, and there were millions of them.

In addition to the six divisions of Marines eventually in the field in the pacific, fifteen US Army division and other Army units fought in the Pacific.

Tarawa, Peleliu, Iwo Jima were "all Marine" operations.