Pacific Ocean theater of World War II in the context of "Pacific Ocean Areas (command)"

The South Seas Mandate, officially the Mandate for the German Possessions in the Pacific Ocean Lying North of the Equator, was a League of Nations mandate in the "South Seas" given to the Empire of Japan by the League of Nations following World War I. The mandate consisted of islands in the north Pacific Ocean that had been part of German New Guinea within the German colonial empire until they were occupied by Japan during World War I. Japan governed the islands under the mandate as part of the Japanese colonial empire until World War II, when the United States captured the islands. The islands then became the United Nations-established Trust Territory of the Pacific Islands governed by the United States. The islands are now part of Palau, the Northern Mariana Islands, the Federated States of Micronesia, and the Republic of the Marshall Islands.

In Japan, the territory is known as "Japanese Mandate for the Governance of the South Seas Islands" (委任統治地域南洋群島, Inin tōchi chiiki nan'yō guntō) and was governed by the Nan'yō Government (南洋廳, Nan'yō-chō).

The Pacific War, sometimes called the Asia–Pacific War or the Pacific Theater, was the theater of World War II fought between the Japan and the Allies in East and Southeast Asia, the Pacific and Indian Oceans, and Oceania. It was geographically the largest theater of the war, including the Pacific Ocean theater, the South West Pacific theater, the Second Sino-Japanese War, and the brief Soviet–Japanese War, and included some of the largest naval battles in history. War between Japan and the Republic of China had begun in 1937, with hostilities dating back to Japan's invasion of Manchuria in 1931, but the Pacific War is more widely accepted to have begun in 1941, when the United States and United Kingdom were brought into the war, after being attacked by Japan.

Japan invaded French Indochina in 1940, and extended its control over the entire territory in July 1941. On 7–8 December 1941, Japan attacked the American naval base at Pearl Harbor in Hawaii; the U.S.-held Philippines, Guam, and Wake Island; and the British colonies of Malaya, Singapore, and Hong Kong, followed by a Japanese declaration of war. The Japanese achieved great success over the next 6 months, allying with Thailand and capturing the listed territories (except for Hawaii) in addition to Borneo, New Britain, the Dutch East Indies, Burma, the Solomon and Gilbert Islands, and parts of New Guinea. In May 1942, Japanese and Allied aircraft carriers fought at the Battle of Coral Sea, resulting in the retreat of a Japanese invasion force headed for Port Moresby. In June, Japan invaded the Aleutian Islands, and in the central Pacific was defeated at the Battle of Midway, considered a key turning point in the war. After this point, the Japanese experienced great difficulty replacing their losses in ships and aircraft as the U.S. produced ever increasing numbers of both.

San Francisco, officially the City and County of San Francisco, is a commercial, financial, and cultural center of Northern California. With an estimated population of 827,526 residents as of 2024, San Francisco proper is the fourth-most populous city in the U.S. state of California and the 17th-most populous in the United States. Among U.S. cities proper with over 300,000 residents, San Francisco is ranked second by population density, first by per capita income, and sixth by aggregate income as of 2023. Depending on how its borders are defined, the broader San Francisco metropolitan area or San Francisco Bay Area is home to 4.6–9.2 million residents. In 2024, the U.S. Census Bureau reported an estimated population of 4,648,486 for the city's metropolitan statistical area (13th-largest in the U.S.) and 9,164,058 residents for the larger combined statistical area (5th-largest).

Prior to European settlement, the modern city proper was inhabited by the Yelamu Ohlone. On June 29, 1776, settlers from New Spain established the Presidio of San Francisco at the Golden Gate, and the Mission San Francisco de Asís a few miles away, both named for Francis of Assisi. The California gold rush of 1849 brought rapid growth, making it the largest city on the West Coast at the time. In 1856, San Francisco became a consolidated city-county. After three-quarters of the city was destroyed by the 1906 earthquake and fire, it was quickly rebuilt, hosting the Panama–Pacific International Exposition nine years later. In World War II, it was a major port of embarkation for naval service members shipping out to the Pacific Theater. After the war, the confluence of returning servicemen, significant immigration, liberalizing attitudes, the rise of the beatnik and hippie countercultures, the sexual revolution, opposition to U.S. involvement in the Vietnam War, and other factors led to the Summer of Love and the gay rights movement, cementing San Francisco as a center of liberal activism.

Fort Mason, in San Francisco, California is a former United States Army post located in the northern Marina District, alongside San Francisco Bay. Fort Mason served as an Army post for more than 100 years, initially as a coastal defense site and subsequently as a military port facility. During World War II, it was the principal port for the Pacific campaign.

Fort Mason originated as a coastal defense site during the American Civil War. The nucleus of the property was owned by John C. Frémont and disputes over compensation by the United States continued into 1968. In 1882 the defenses were named for Richard Barnes Mason, a military governor before statehood. Fort Mason became the headquarters for an Army command that included California and the Hawaiian Islands from 1904 to 1907. In 1912 the Army began building a port facility with piers and warehouses to be a home base for ships of the Army Transport Service serving Alaska, Hawaii, the Philippines and other Pacific Army posts and focus of Army supply for the Pacific.

The Battle of Wake Island was a battle of the Pacific campaign of World War II, fought on Wake Island. The assault began simultaneously with the attack on Pearl Harbor naval and air bases in Hawaii on the morning of 8 December 1941 (7 December in Hawaii), and ended on 23 December, with the surrender of American forces to the Empire of Japan. It was fought on and around the atoll formed by Wake Island and its minor islets of Peale and Wilkes Islands by the air, land, and naval forces of the Japanese Empire against those of the United States, with marines playing a prominent role on both sides.

The battle started with a surprise bombing raid on 8 December 1941, within hours of Pearl Harbor, and the air raids continued almost every day for the duration of the battle. There were two amphibious assaults, one on 11 December 1941 (which was rebuffed) and another on 23 December, that led to the Japanese capture of the atoll. In addition, there were several air battles above and around Wake and an encounter between two naval vessels. The U.S. lost control of the island and 12 fighter aircraft; in addition to the garrison being taken as prisoners of war, nearly 1,200 civilian contractors were also captured by the Japanese. The Japanese lost about two dozen aircraft of different types, four surface vessels, and two submarines as part of the operation, in addition to at least 600 armed forces. It is typically noted that 98 civilian POWs captured in this battle were used for slave labor and then executed on Wake Island in October 1943. The other POWs were deported and sent to prisoner of war camps in Asia, with five executed on the sea voyage.

PT-109 was an 80-foot (24 m) Elco PT boat (patrol torpedo boat) last commanded by Lieutenant (junior grade) John F. Kennedy, future United States president, in the Solomon Islands campaign of the Pacific theater during World War II. Kennedy's actions in saving his surviving crew after PT-109 was rammed and sunk by a Japanese destroyer earned him several commendations and made him a war hero. Back problems stemming from the incident required months of hospitalization at Chelsea Naval Hospital and plagued him the rest of his life. Kennedy's postwar campaigns for elected office often referred to his service on PT-109.

The Battle of Midway was a major naval battle in the Pacific Theater of World War II that took place on 4–7 June 1942, six months after Japan's attack on Pearl Harbor and one month after the Battle of the Coral Sea. The Japanese Combined Fleet under the command of Isoroku Yamamoto suffered a decisive defeat by the U.S. Pacific Fleet near Midway Atoll, about 1,300 mi (1,100 nmi; 2,100 km) northwest of Oahu. Yamamoto had intended to capture Midway and lure out and destroy the U.S. Pacific Fleet, especially the aircraft carriers which had escaped damage at Pearl Harbor.

Before the battle, Japan desired to extend its Pacific defense perimeter, especially after the Doolittle air raid of Tokyo in April 1942, and to clear the seas for attacks on Midway, Fiji, Samoa, and Hawaii. A related Japanese attack on the Aleutian Islands began one day earlier, on 3 June. The Japanese strike force at Midway, known as the Kidō Butai, was commanded by Chuichi Nagumo. Yamamoto's plan for the operation, which depended on precise timing and coordination, was undermined by its wide dispersal of forces, which left the rest of the fleet unable to support the Kidō Butai effectively.

The 7th Infantry Division is a non-deployable administrative headquarters of the United States Army based at Joint Base Lewis-McChord. It is charged with maintaining the capability of two Stryker infantry brigade combat teams, a combat aviation brigade, and a Division Artillery Unit, as well as preparing units for several U.S. Army Pacific yearly exercises. The 7th Infantry Division is the only active-duty multi-component division headquarters in the Army. Brigadier General Bernard J. Harrington commands the division. The 7th Infantry Division is also home to two of the Army's newest enabling battlefield capabilities, the Multi Domain Task Force and the Intelligence, Information, Cyber, Electronic Warfare and Space Capabilities, or I2CEWS battalion.

The division was first activated in December 1917 in World War I, and has been based at Fort Ord, California for most of its history. Although elements of the division saw brief active service in World War I, it is best known for its participation in the Pacific Ocean theater of World War II where it took heavy casualties engaging the Imperial Japanese Army in the Aleutian Islands, Leyte, and Okinawa. Following the Japanese surrender in 1945, the division was stationed in Japan and Korea, and with the outbreak of the Korean War in 1950 was one of the first units in action. It took part in the Inchon Landings and the advance north until Chinese forces counter-attacked and almost overwhelmed the scattered division. The 7th later went on to fight in the Battle of Pork Chop Hill and the Battle of Old Baldy.

The Pacific War, sometimes called the Asia–Pacific War or the Pacific Theater, was the theater of World War II fought between Japan and the Allies in East and Southeast Asia, the Pacific and Indian Oceans, and Oceania. It was geographically the largest theater of the war, including the Pacific Ocean theater, the South West Pacific theater, the Second Sino-Japanese War, and the brief Soviet–Japanese War, and included some of the largest naval battles in history. War between Japan and the Republic of China had begun in 1937, with hostilities dating back to Japan's invasion of Manchuria in 1931, but the Pacific War is more widely accepted to have begun in 1941, when the United States and United Kingdom were brought into the war, after being attacked by Japan.

Japan invaded French Indochina in 1940, and extended its control over the entire territory in July 1941. On 7–8 December 1941, Japan attacked the American naval base at Pearl Harbor in Hawaii; the U.S.-held Philippines, Guam, and Wake Island; and the British colonies of Malaya, Singapore, and Hong Kong, followed by a Japanese declaration of war. The Japanese achieved great success over the next 6 months, allying with Thailand and capturing the listed territories (except for Hawaii) in addition to Borneo, New Britain, the Dutch East Indies, Burma, the Solomon and Gilbert Islands, and parts of New Guinea. In May 1942, Japanese and Allied aircraft carriers fought at the Battle of Coral Sea, resulting in the retreat of a Japanese invasion force headed for Port Moresby. In June, Japan invaded the Aleutian Islands, and in the central Pacific was defeated at the Battle of Midway, considered a key turning point in the war. After this point, the Japanese experienced great difficulty replacing their losses in ships and aircraft as the U.S. produced ever increasing numbers of both.