The Japanese conquest of Guam began about an hour after the attack on Pearl Harbor, when Saipan based Japanese dive bombers launched the first in a series of raids on the island.
At that time Guam’s total protection consisted of 153 Marines, 271 US Navy personnel, 134 civilian construction workers, and 247 members of the local Chamorro Insular Force Guard and the Naval Militia. (Chamorros are the indigenous people of Guam).
The garrison had no artillery, only a few .30- caliber machine guns, and various small arms. For two days the Japanese bombed and strafed the island and its defenders.
In the early morning hours of December 10, a special Japanese naval landing party of about 400 men from the 5 th Defense Force based on Saipan began landing at Dungca’s Beach in Agana Bay.
At the same time, a Japanese army unit known as the South Seas detachment landed on beaches of Aporguan, Tumon, Togcha, Agat, and other areas. The Insular Guard made a valiant attempt to stop the Japanese advance at the Plaza de Espana in Agana (now known as Hagatna) but was soon driven back. By 5:45 a.m., Captain George J. McMillin, USN, the island’s governor, realized that his tiny command was no match for the invasion force and began to surrender his post and the island.