By the beginning of 1944, United States Marine forces had already made a start on the conquest of areas overrun by the Japanese early in World War II. Successful American assaults in the Southwest Pacific, beginning with Guadalcanal in the Solomon Islands in August 1942, and in the Central Pacific at Tarawa in the Gilbert Islands in November 1943, were crucial battles to mark the turn of the Japanese conquest. The time had now come to take one more decisive step: assault of the islands held by Japan before 1941.
These islands, that were gave to the Japanese by the League of Nations after World War I, were a source of mystery. Outsiders were barred; illegal fortifications were presumed; yet any Central Pacific drive towards Japan's inner defense ring had to confront these unknowns. The obvious target to begin with was the Marshall Islands. As early as 1921 a Marine planning officer had pinpointed their geographic significance.
The Marshall Islands or were once called the Marshalls'. Consisted of 32 atolls, more than 1,000 islands, and 867 reefs. Kwajalein which is part of the Marshalls’ is the largest atoll in the world, 60 miles long and 20 miles wide, a semi-enclosed series of 80 reefs and small islands around a huge lagoon of some 800 square miles. Located 620 miles northwest of Tarawa, which Marines also invaded and retook in 1943 during World War two, (At Tarawa, for example, more than 3,300 men had been killed or wounded in as little as 76 hours.) Tarawa is also 2,415 miles southwest of Pearl Harbor, so by capturing Kwajalein it would have far-reaching significance in that it would break the outer ring of Japanese Pacific defense lines.
So after the Joint Staff had came up with a strategy they decided that the 4th Marine Division under Major General Harry Schmidt was to lead the assault on Roi-Namur, and the Army 7th Infantry Division under Major General Charles H. Corlett would attack Kwajalein. After these islands were taken, there