Pacific War
In 1931, Japan invaded Manchuria without declaring war. This action sought raw materials to fuel its growing industrial economy. By 1937, the Marco Polo Bridge Incident provoked full-scale war between China and Japan. The Nationalist Party and Chinese Communists suspended their civil war to form a nominal alliance against Japan. Generalissimo Chiang Kai-shek deployed his best troops to defend Shanghai against some 300,000 Japanese troops. The city fell after three months of fighting. In mid-December 1937, the Japanese captured Nanjing and committed atrocities in the Nanjing Massacre. Between 200,000 and 300,000 civilians and prisoners of war were murdered by the Japanese Army.
Tensions with the West grew as early as 1935 when Japanese strategists identified Dutch East Indies oil reserves as crucial for expansion. By 1940, Western powers including Australia, the US, Britain, and the Dutch government stopped selling oil, iron ore, and steel to Japan. Imported oil made up about 80% of domestic consumption. Without these resources, Japan's economy would grind to a halt. The Japanese media began referring to these embargoes as the ABCD line. In April or May 1941, the Imperial General Headquarters began planning for war with the Western powers. Japan increased its naval budget and placed large formations of the Army under the command of the Imperial Japanese Navy.
In the early hours of the 7th of December Hawaiian time, carrier-based Japanese aircraft launched a surprise air strike on Pearl Harbor. This attack knocked eight American battleships out of action and destroyed 188 American aircraft. The assault killed 2,403 Americans. The Japanese believed that such a sudden blow would force the United States to agree to a negotiated settlement. However, three American aircraft carriers remained at sea during the attack. Vital naval infrastructure and signals intelligence units were unscathed.
Concurrent attacks struck British territories in Malaya, Singapore, and Hong Kong. Thailand surrendered within hours of invasion before formally allying with Japan on the 21st of December. On the 15th of February 1942, Allied forces in Singapore surrendered to the Japanese. About 130,000 Indian, British, Australian, and Dutch personnel became prisoners of war. Japanese aircraft bombed Darwin, Australia, on the 19th of February 1942, killing at least 243 people. Over the following 19 months, Australia was attacked from the air by the Japanese almost 100 times. In late May 1942, IJN midget submarines launched a raid on Sydney Harbour.
The Battle of Midway began on the 3rd of June when American aircraft spotted the Japanese transport group west of the atoll. On the 4th of June, American SBD Dauntless dive bombers surprised and destroyed three Japanese carriers: Sōryū, Kaga, and Akagi. A single carrier, Hiryū, launched a counterattack that put Yorktown out of action. Later in the afternoon, aircraft from two remaining American carriers found and destroyed Hiryū. With the striking power of the Kido Butai destroyed, Japan's offensive naval power was significantly blunted.
In August 1942, 16,000 US Marines landed on Guadalcanal and Tulagi. Vice Admiral Gunichi Mikawa sank four Allied heavy cruisers in the Battle of Savo Island but failed to attack vulnerable transport ships. Over six months, both sides poured resources into an escalating battle of attrition. By late 1942, the Japanese decided to abandon Guadalcanal. They evacuated their troops in February 1943. Over 25,000 Japanese soldiers died on Guadalcanal, with 15,000 having starved to death. This victory provided a significant boost to Allied morale.
Allied forces began a protracted offensive campaign across the Pacific theater in June 1943. Operation Cartwheel initiated amphibious invasions to recapture the Solomon Islands and New Guinea. The goal was to isolate the major Japanese forward base at Rabaul. Landings secured the Treasury Islands and placed Allied troops on Choiseul, Bougainville, and Cape Gloucester. In November 1943, US Marine forces overwhelmed a 4,500-strong Japanese garrison at Tarawa Atoll. This experience drove the Allies to improve techniques of amphibious landings.
Operations in the Gilbert Islands were followed by landings on the Marshall Islands in January and February 1944. American submarines played a major role in defeating Japan despite making up less than two percent of Allied navies. Submarines strangled Japanese commercial and military shipping, cutting off nearly all oil imports essential to weapons production. By early 1945, Japanese oil supplies were so limited that the remaining IJN fleet was virtually stranded in their anchorages. Allied submarine forces destroyed 1,200 Japanese merchant ships totaling about five million tons of shipping.
American submarines operated out of bases at Cavite, Fremantle, Brisbane, Pearl Harbor, Trincomalee, Midway, and later Guam. Within hours of Pearl Harbor, Roosevelt promulgated unrestricted submarine warfare against Japanese shipping. This meant sinking any warship or commercial vessel without warning. The standard-issue Mark 14 torpedo proved defective until September 1943. In 1944, the US Navy restructured its submarine fleet, installing effective shipboard radar on 150 submarines.
Allied submarines accounted for 56% of Japanese merchantmen sunk. Mines or air attack destroyed most of the rest. Over 200 IJN warships were sunk, including eight carriers. Underwater warfare was especially dangerous; 3,500 American submariners never returned from patrol. This represented a 22 percent casualty rate, the highest of any American force in World War II. By early 1945, fuel shortages rendered the Japanese fleet unable to withdraw to safety regardless of battle outcomes.
In mid-1944, Japan launched Operation Ichi-Go with over 500,000 troops on the Chinese mainland. Despite tactical victories, the operation failed to provide significant strategic gains. A majority of Chinese forces retreated out of the area and later attacked Japanese positions at the Battle of West Hunan. In India, Lieutenant General Renya Mutaguchi's offensive into Burma ended in July 1944. The Japanese lost over 50,000 troops, mainly to starvation and disease. This marked the worst defeat suffered by the IJA to that date.
The invasions of Iwo Jima and Okinawa occurred between June 1944 and June 1945. These operations enabled a blockade of the Japanese home islands and started a strategic air raid campaign causing widespread urban destruction. On the 6th of August 1945, the U.S. dropped an atomic bomb on Hiroshima. A second bomb fell on Nagasaki on the 9th of August 1945. The Soviet Union invaded Manchuria on the 9th of August. Japan surrendered unconditionally on the 15th of August and signed a surrender document on the 2nd of September.
Common questions
When did Japan invade Manchuria without declaring war?
Japan invaded Manchuria in 1931 without declaring war. This action sought raw materials to fuel its growing industrial economy.
What happened during the Nanjing Massacre in December 1937?
The Japanese captured Nanjing on the 15th of December 1937 and committed atrocities known as the Nanjing Massacre. Between 200,000 and 300,000 civilians and prisoners of war were murdered by the Japanese Army.
Why did Japan attack Pearl Harbor on the 7th of December 1941?
Western powers including Australia, the US, Britain, and the Dutch government stopped selling oil, iron ore, and steel to Japan by 1940. The Japanese believed that a sudden blow would force the United States to agree to a negotiated settlement.
How many American sailors died at Pearl Harbor on the 7th of December 1941?
The assault killed 2,403 Americans during the surprise air strike on Pearl Harbor. Eight American battleships were knocked out of action and 188 American aircraft were destroyed.
When did Allied forces surrender in Singapore during World War II?
Allied forces in Singapore surrendered to the Japanese on the 15th of February 1942. About 130,000 Indian, British, Australian, and Dutch personnel became prisoners of war.
What was the result of the Battle of Midway starting on the 3rd of June 1942?
American SBD Dauntless dive bombers surprised and destroyed three Japanese carriers on the 4th of June 1942. With the striking power of the Kido Butai destroyed, Japan's offensive naval power was significantly blunted.