The Marshall Islands, officially the Republic of the Marshall Islands, is an island nation located within Micronesia that is comprised of 29 atolls, themselves made up of over 1,000 individual islands and islets. The Marshall Islands were the location of several battles between the United States and Japan during World War II, after which the islands were captured and occupied by the United States. During the early part of the Cold War, the United States carried out 67 nuclear weapon tests in the Marshall Islands between 1946 and 1958, most notably the Castle Bravo test conducted at Bikini Atoll in 1954. Due to their association with nuclear testing, the Marshall Islands are frequently referenced in Godzilla films.
According to Dr. Kyohei Yamane, the Castle Bravo hydrogen bomb test conducted at Bikini Atoll, an atoll located within the Marshall Islands, in March 1954 awakened the monster Godzilla from his slumber in a deep underwater cavern. The explosion completely destroyed Godzilla's habitat and killed any other members of his species that lived with him, and also severely burned and irradiated him. Enraged, Godzilla swam to the surface and began attacking fishing boats.
In 1944, the United States military invaded the Marshall Islands, eliminating the Japanese garrisons located there. After the Americans had seized the island of Kwajalein, the only Japanese garrison remaining was the one located on the small neighboring island of Lagos. The garrison, led by Major Yasuaki Shindo, refused to surrender despite constant bombardment from the American Navy, and planned a desperate last charge against the Americans. The Japanese garrison launched its attack early in the morning, but was overwhelmed by the American forces. However, a gigantic dinosaur emerged from the jungle, terrifying the American soldiers, who opened fire on it. The dinosaur retaliated, killing the soldiers and approaching the shore. There, it was seemingly brought down by artillery from nearby American battleships, but when infantry surrounded it it rose back to its feet and trampled them to death. The dinosaur then returned to the jungles of the island, leaving the Americans in retreat and Japanese garrison intact. Later, the wounded dinosaur collapsed in the jungle from its wounds. Shindo and his garrison surrounded the dinosaur, thanking it for saving their lives and saluting it before finally leaving the island.
All of these events had been witnessed by a group of time travelers who had come back to the past believing the dinosaur would be exposed to the Castle Bravo test conducted at nearby Bikini Atoll ten years later and transform into Godzilla. Using the time travelers' ship KIDS, Emmy Kano and her android M11 teleported the wounded dinosaur to the Bering Sea, believing it would eventually die there. In the dinosaur's place, Emmy left behind three genetically-engineered creatures called Dorats. In 1954, the Castle Bravo test mutated the Dorats into the monster King Ghidorah, which Emmy's cohorts took control of in 1992 and used to force the Japanese government to surrender to them.
In 1954, an American nuclear submarine accidentally awakened a giant prehistoric monster called Godzilla, which began attacking American and Soviet submarines in the Pacific Ocean. To try and stop the creature, the United States exploited his attraction to nuclear material by preparing the Castle Bravo nuclear warhead at Bikini Atoll, drawing Godzilla to the island. When Godzilla reached the island, the bomb was detonated in an attempt to kill him. The bomb failed to kill Godzilla, but the monster returned to his hibernation for another 60 years.