When Europe and its far-flung colonies went to war in 1939, America's territories in the Pacific and Alaska were but lightly defended. On Guam, the navy had previously removed the six 7-inch coastal guns that had been mounted on Mount Tenjo and on Orote Peninsula, both batteries having offered modest protection to the small navy yard in Apra Harbor. In 1938, the U.S. Congress appropriated funds for naval air stations and submarine bases in Alaska, Hawaii, Midway, and Wake, but voted against defenses for Guam. In December 1941, Capt George J. McMillin, USN, governor of Guam and commandant of the naval station, had under his command 41 naval personnel, 153 marines, and 80 Guamanians of the Insular Force Guard. Most of the marines were garrisoned at Sumay on Orote Peninsula, while others served as constabulary in the several villages. Weaponry consisted or rifles, pistols, and .30 caliber machine guns.
Shortly after the Japanese attack on Pearl Harbor (Monday, December 8, on Guam), Japanese aircraft from nearby Saipan made their first air raid on Guam, bombing and strafing naval installations, roads, and villages. The planes returned the next day, continuing the attack on Agana, the capital, and other targets. Before dawn, December 10, 400 Japanese naval troops ol a Special Naval Landing Force from Saipan landed at Dungcas Beach two miles northeast of Agana and marched toward the capital.
Although Guamanians of the Insular Force put up resistance at the. Plaza de Espana, Captain McMillin realized the futility of the situation arid surrendered at 6 a.m. Also on this morning, about 5,000 Japanese army troops landed at various points, particularly on the beaches south of Agat village, and quickly overran the lowland north to Agana. 
The army troops left Guam early in 1942 for duty at the front in the Southwest Pacific. The Empire was on the march, and Guam was now far behind the line of battle. Only 150 naval troops of the 54th Keibitai remained on the island. Not until Admiral Chester W. Nimitz's Central Pacific campaign got underway in late 1943, did the Japanese intensify construction of Guam's fortifications. To a degree, this situation was found on Japan's other rear islands in the Central Pacific. Surviving defensive works on these former Japanese Mandates, however, are generally more substantial than those found on Guam--which makes those on Guam all the more valuable for commemorating its World War II history. On Guam, pillboxes and coastal batteries were constructed with reinforced concrete, coconut palm logs, sandbags, earth, or coral rock. Most of these works were palm log. No concrete blockhouses or large bombproof structures, such as the Japanese constructed on other islands, were erected.
Earlyh in 1944, Japan moved reinforcements into the Marianas. By summer, Japanese army and naval forces on Guam totaled 18,500, including two naval construction battalions as well as army engineers. In addition, the Japanese impressed Guamanian men as laborers on the defensive works. The Japanese commander, Lt. Gen. Takeshi Takashima, arranged the principal coastal defenses along Guam's western beaches, from Tumon Bay to Piti, north of Apra Harbor; and on Orote Peninsula and the Agat area south of the harbor. By June 1944, Japan had not yet conceived of a defense in depth for defending an island. Consequently, only a few inland positions on Guam were developed as fortified points. After the liberation of Guam in 1944, American intelligence officers made the following observations on the Japanese defenses: many were hastily constructed and often incomplete; there was limited defense in depth and few works were sited on the high ground; no protection was provided on the flanks and rear; fields of fire were restricted; and there was no mass fire of artillery.
An American task force invaded Saipan June 15, 1944, and declared that island secured on July 9. The invasion of Guam was first set for June 18, but was postponed until July 21 for two reasons: The tenacious Japanese defense of Saipan resulted in the American decision to add an army division to the U.S. Marine force for the landings on Guam, which division was still in Hawaii. During the fighting on Saipan, American naval forces were diverted to do battle with a Japanese fleet in the Philippine Sea on June 19 and 20. This delay was of some advantage to both sides. It allowed American naval and air forces additional time to conduct massive bombings and bombardments of Guam's defenses. For the Japanese, the delay allowed time to concentrate troops and armament at the beaches they now knew the Americans would assault--the western beaches flankimg Apra Harbor.
Last Updated: 07-Mar-2005