Pearl Harbor Timeline
1931–32 Japan establishes the puppet state of Manchuria
March 25 Japan withdrew from League of Nations
November 25 Japan signs Anti-Comintern Pact with Germany
December 2 - Yamamoto begins forging the naval air arm into a modern weapon.
July 7 Japan begins general attack on China; known as the China Incident
February 10 - Japan occupies the Chinese island of Hainan.
July 2 Japanese forces in Manchuria cross into Outer Mongolia; known as the Nomonhan
August - Adm. Isoroku Yamamoto appointed commander-in-chief of the Imperial Japanese Navy.
September 4 - Yamamoto writes to V/Adm. Shimata to say that he is uneasy about “Japan’s relations with Germany and Italy in the face of changes now taking place in Europe.”
September 16 Ceasefire with Soviet forces in Manchuria
Spring - The US fleet transfers to Pearl Harbor as its permanent home base: to the Japanese, this is a thinly veiled threat. Yamamoto uses this to urge expansion of naval air power. Yamamoto begins thinking that it would be better to carry war to the US Navy rather than wait for them to choose the time and place for battle.
July - Roosevelt has an embargo placed on all aviation fuel, steel and scrap iron to Japan.
August - Lieutenant-Colonel Friedman, a cryptographer, breaks the Japanese Purple Code (MAGIC).
September 3 - Roosevelt gives Britain 50 old destroyers for the right to establish US naval bases in British territories.
September 4 - The US warns Japan not to attack French Indochina.
September 11 - Ojiro Okuda is appointed acting consul general to Hawaii. He is in charge of reporting on movements of US ships in the harbor, much of which appears in American newspapers. Kohichi Seki studies Jane’s Fighting Ships and travels around the island studying the base and airfields, but without trespassing on US government property though.
September 22 Japan granted bases in Indo-China
September 27 Tripartite Pact between Germany, Italy, and Japan
November 12 - British torpedo bombers attack the Italian fleet at Taranto, disabling half of Italy’s Mediterranean fleet.
December 10 - Yamamoto writes to Shimada: “The probability is great … our operations against the Netherlands’ Indies are almost certain to develop into a war with America, Britain and Holland before those operations are half-over. Consequently we should not launch … the southern operation unless we are prepared … and adequately equipped.”
December 30 - Rear Admiral Bloch sends a memo: “Any aircraft attacking Pearl Harbor will … be brought by carriers.”
January 1 - In Japan, American ambassador Grew writes in his diary: “Japan … is on the warpath … If … Americans … could read … articles by leading Japanese … they … would realize the utter hopelessness of a policy of appeasement.”
January 6 - President Roosevelt declares the United States the “arsenal of democracy.”
January 7 - Yamamoto writes a letter to R/Adm. Takijiru Oikawa, saying: “A conflict with the United States … is inevitable.” The Japanese Navy should “destroy the US main fleet at the outset of the war.” He continues that the Japanese Navy should strike so as to “decide the fate of the war on the very first day.” His plan is to find the US Navy “at Pearl Harbor [and] attack it vigorously with our air force.” He concludes that if the US Navy is not at Pearl Harbor, they should find them regardless of where they are. The Japanese First and Second Carrier Divisions should mount a “surprise attack with all their air strength, risking themselves on a moonlight night or at dawn.” Oilers were needed for refueling at sea, destroyers would pick up survivors whose aircraft or ships went down, and submarines would attack vessels fleeing Pearl Harbor and attempt to sink Allied vessels at the entrance and block it. An attack on “the Philippines and Singapore should be made at almost the same time as … against Hawaii.” At the end of the letter, Yamamoto requests: “I sincerely desire to … personally command that attack force.”
January 24 - Prince Fumimaro Konoye, the Japanese prime minister, asserts that “firm establishment of a Mutual Prosperity Sphere in Greater East Asia is … necessary to the continued existence of this country.” Yamamoto hypothesizes that should war break out “between Japan and the United States, it would not be enough that we take Guam and the Philippines, nor even Hawaii and San Francisco. We would have to … dictate the terms of peace in the White House. I wonder if our politicians … are prepared to make the necessary sacrifices.”
January 27 - In secret talks with Britain, the US decides that if Japan enters the war on the German side, and if the US enters the war, Germany is to be defeated first, then Japan. Ambassador Grew, in Japan, is warned by his Peruvian counterpart that he has heard a Japanese worker in his embassy say that if war occurs the “Japanese military … [will] attempt a surprise mass attack on Pearl Harbor using all their military facilities.” In Washington, military intelligence is surprised only that Grew puts credence in the source of the report and not in the supposition of the report. In Japan, Foreign Minister Yosuke Matsuoka says, “We must control the Western Pacific,” and that the US should reconsider their prior actions: if the US does not, there is “no hope for Japanese–American relations.” Aboard Nagato, Yamamoto discusses the logical and technical feasibility of an attack on Pearl Harbor. After this meeting, Onishi asks Maeda (his senior staff officer) the following question: if US capital ships were “moored around Ford Island, could a successful torpedo attack be launched against them?” Maeda says no, the water is too shallow for torpedoes to be effective. However, if the torpedoes were modified…
February 1 - Kimmel replaces Richardson as CinCPAC; Short is promoted to commander of the Hawaiian Department.
February 5 - Kimmel receives a letter from Secretary Knox stating: “If war eventuates with Japan … hostilities … would start … with a surprise attack on Pearl Harbor.” The letter tells Kimmel to “increase the joint readiness of the army and navy to withstand a raid.” He says that probable forms of attack are bombing, torpedo attacks, or both. Congressman Faddis of Pennsylvania states: “The Japanese are not going to risk a fight … where they must face the American Navy in open battle. Their navy is not strong enough.”
February 12 - Nomura presents his credentials, which appoint him Ambassador to Washington, to Cordell Hull.
February 15 - Kimmel issues a Pacific Fleet Conference letter saying they are faced with a possible surprise attack on ships in Pearl Harbor.
Mid-February - Onishi sends for Cmdr Minoru Genda and presents Yamamoto’s plan, mentioning that Yamamoto has given some thought to making it a one-way mission (katamechi kogami) to increase the striking distance to over 500 miles. Genda opposes treating aircraft as disposable: “Ditching … would be a waste of men and planes.” He thinks Yamamoto should include dive-bombers and high altitude bombers as well as torpedo planes in the attack. “To obtain the best results, all carriers should approach as close to Pearl Harbor as possible.” His last point is: “Our prime target should be US carriers.” Onishi asks Genda to prepare a report about feasibility, component forces and manner of execution, and then report back in ten days.
Late February - Genda gives Onishi a report containing ten main proposals. It must be a surprise attack; US carriers are its main objective; US aircraft on Oahu are an objective; and every available Japanese carrier should take part in the operation. Furthermore, all kinds of attack aircraft should be used, and Japanese fighters should play an active role in the attack; the attack should be in early morning; refueling vessels at sea is necessary for success; and all planning must be ultra-secret. The tenth proposal is for a full-scale invasion, which Onishi disagrees with because they could not maintain supply so far from their present bases. Yamamoto wants to cripple the US Navy whereas Genda feels they should annihilate it.
February 27 - Okuda reports: “The fleet goes to sea for a week and stays in Pearl Harbor for one week. Every Wednesday those at sea and those in the harbor change places.”
March 5 - The Japanese foreign ministry wires Nomura to say that they feel fairly certain that the US “is reading your code messages.”
March 10 - Onishi gives Yamamoto a draft of his plan for attack, based on Genda’s plan but with some modifications.
March 11–12 - Congress passes the Lend Lease Act, which supplies materiel to governments fighting the Axis.
March 14 - Kita is appointed consul general to Hawaii.
March 20 - Nomura responds to the foreign ministry: “Though I do not know which ones, I have discovered that the United States is reading some of our codes.” Nomura informs them he will tell them details in a “safe” way. Still they did not change the Purple Code. Matsuoka may have been suspicious of Nomura’s warning, feeling it sprang from insecurity.
March 27 - Takeo Yoshikawa, an intelligence officer, arrives in Pearl Harbor and realizes that battleships are berthed in pairs and that the in-shore ship is protected from torpedo attacks by the outboard one.
March 30 - Roosevelt orders the Coast Guard to seize two German, 28 Italian and 35 Danish ships in US ports.
April 1 - Naval Intelligence in Washington alerts district commanders to the fact that “the Axis Powers often … [attack on] Saturday and Sunday or on national holidays” and that commanders should put “proper watches and precautions … in effect.”
April 10 - The IJN reorganizes into the 1st Air Fleet, consisting of the First Carrier Division (Kaga and Akagi and four destroyers), the Second Carrier Division (Hiryu and Soryu and four destroyers) and the Fourth Carrier Division (Ryuho and two destroyers).
April 13 - Japan and Russia sign a neutrality pact giving Japan the green light for southward expansion.
April 15 - The US begins shipping lend-lease goods to China.
April 21 - US, English, and Dutch officers coordinate the proposed roles of each in the military defense against Japan in case of a Japanese attack on Singapore.
April 23 - Marshall disagrees with Roosevelt’s decision to keep the US fleet in Hawaii because “our heavy bombers and … pursuit planes … could put up such a defense that the Japs wouldn’t dare attack Hawaii.”
April 28 - When queried about the US choice to strengthen the Atlantic Fleet by removing vessels from the Pacific, the British reply that the “reduction … would not unduly encourage Japan.” New Mexico, Mississippi, Idaho, Yorktown, four light cruisers, 17 destroyers, three oilers, three transports, and ten auxiliaries are transferred by the end of summer.
May 20 - Nomura confirms to Tokyo: “the US is reading some of our codes.”
May 26 - Yoshikawa reports that three battleships and three light cruisers have disappeared from Pearl Harbor. Kimmel fires off an 11-page memo noting that 72 percent of the new officers for the Atlantic came from the Pacific Fleet and that the Pacific Fleet’s needs are subordinated to those of Britain and the Atlantic Fleet.
May 27 - Roosevelt declares the US to be in an unlimited state of national emergency.
June 14 - The US freezes German and Italian assets.
June 16 - German consulates in the US are shut down.
June 17 - Germany moves against US property in Germany.
June 20 - The US stops oil shipments from Gulf and East Coast ports to all destinations except Latin America and Britain.
June 22 - Italian consulates in the US are closed.
June 26 - Vichy France permits Japan to occupy French Indochina. The US impounds Japanese credits in the US. Roosevelt nationalizes the Philippine Army.
July 17 - A new Japanese government is formed.
July 26 American government freezes Japanese assets in the USA; General MacArthur appointed to command US Army in Far East based in the Philippines
July 28 - The US puts an embargo on oil sales, freezes assets, and closes ports to Japanese vessels.
August 18 - An amendment to the 1940 Selective Service Law extends the length of service for US inductees from one year to two-and-a-half years.
September 24 - A message from Tokyo to the Consulate General instructs the spy to report on US vessels in Pearl Harbor.
October 16 - Konoye resigns and Gen. Tojo sets up a new government with himself as prime minister. Stark warns Kimmel of the possibility of Japanese activities.
October 17 General Tojo becomes Prime Minister of Japan
November 5 - Yamamoto issues Top Secret Order No.1 to the Combined Fleet, detailing the plan for the attack on Pearl Harbor.
November 7 - Congress repeals sections of the Neutrality Act concerning arming US cargo ships and transporting war goods to warring nations.
November 10 - Britain states that should Japan go to war with the US, they will declare war on Japan “within the hour.”
November 22 - The US intercepts a message telling Nomura that the deadline of November 22 has been extended to November 25, 1941.
November 25 - No US–Japanese agreement is reached: consequently, Nagumo’s task force sails from the Kuriles.
November 27 - Argentina decides not to sell tungsten to Japan. Kimmel and Short are advised that US–Japanese negotiations have failed and that they should be prepared for any eventuality. Kimmel is ordered to deliver 25 aircraft to Wake and Midway.
December 2 - Nagumo gets the go-ahead. The US intercepts a message to the Japanese Embassy to destroy all codes.
December 6 - Roosevelt is given the partly deciphered 14-part message. Instructions state it is not to be given to Hull until 1300 hrs Washington time on December 7.
December 7–8 Japanese attack Malaya, Pearl Harbor, and the Philippines
December 8 - Roosevelt calls the attack on Pearl Harbor a day that will “live in infamy,” and Congress declares war on Japan. Gen. Yamashita’s 25th Army lands near the borders of Thailand and Malaya and begins the battle for Singapore.
December 10 Prince of Wales and Repulse sunk; main Japanese landing in the Philippines
December 11 - Italy and Germany declare war on the US.
December 12 - Japanese forces occupy Guam.
December 14 Japanese begin invasion of Burma
December 23 Wake Island captured by Japanese
December 25 Surrender of Hong Kong
January 23 Japanese forces attack Rabaul
January 30 Japanese forces attack Ambon
February 15 Singapore Island surrenders
February 19 Japanese bomb Darwin, Australia
February 19–20 Japanese forces land on Timor
February 27 Naval battle of Java Sea
February 28 Japanese forces land in Java
March 8 Japanese troops enter Rangoon; Japanese land in New Guinea
March 17 MacArthur appointed to command Southwest Pacific Area
April 9 American forces on Bataan surrender and begin the infamous Bataan Death March
April 18 Doolittle raid on Tokyo
May 5–8 Battle of the Coral Sea
May 6 American forces on Corregidor surrender
May 20 Allied forces withdraw from Burma
May 31 Attack on Sydney Harbour
June 4–6 Battle of Midway Island; considered the turning point for the war in the pacific
June 7 Japanese land in Aleutian Islands
July 21 Japanese land at Gona area, Papua
August 7 Americans land in Solomons
August 8–9 Naval battle of Savo Island
August 25–26 Japanese land at Milne Bay
Late September Japanese drive over Owen Stanley Range halted
November 12–15 Naval battle of Guadalcanal
December First Arakan offensive begins
January 23 Organized Japanese resistance in Papua ends
February 7 Last Japanese withdraw from Guadalcanal
February 13 First Chindit operation into Burma
March 2–4 Battle of the Bismarck Sea
April 18 Death of Admiral Yamamoto
May End of the First Arakan offensive
May 11 American forces land on Attu in Aleutian Islands
June 30 Americans land on New Georgia
September 4 Australians land near Lae, New Guinea
November Second Arakan offensive begins
November 1 American troops land on Bougainville, northern Solomons
November 15 Mountbatten takes command of South-East Asia Command
November 20 American forces invade Makin and Tarawa in Gilberts
December 15 Americans land on New Britain
January 31 Americans invade Marshall Islands
February 4 Japanese Arakan offensive, Ha-Go, begins
February 15 New Zealand forces invade Green Island
February 29 Americans invade Admiralty Islands
March 2 Second Chindit operation launched into Burma
March 15 Japanese Imphal offensive, U-Go, begins
April 22 Americans land at Hollandia and Aitape
May 27 Americans land on Biak Island
June 15 Americans invade Saipan in the Marianas; American strategic air offensive against Japan begins from China
June 19–20 Battle of the Philippine Sea
June 22 Siege of Imphal is broken
July 2 Americans land on Noemfoor
July 18 General Tojo falls from power as Japanese Prime Minister
July 21 Americans invade Guam
September 15 Americans land in Palau Islands (Peleliu) and on Morotai in the Halmaheras
October 10 US Third Fleet attacks Okinawa
October 20 Americans land on Leyte
October 23–26 Naval battle of Leyte Gulf
November 24 Superfortresses attack Japan from bases in the Marianas
December Final Arakan offensive begins
December Operation Extended Capital begins in Burma
January 9 American forces land on Luzon
February 19 American forces land on Iwo Jima
March 9–10 First fire-bomb attack on Tokyo
March 10 American forces land on Mindanao
March 20 British capture Mandalay
April 1 American forces land on Okinawa
May 1 Australians invade Tarakan
May 3 British troops capture Rangoon
August 6 Atomic bomb dropped on Hiroshima
August 9 Atomic bomb dropped on Nagasaki; Soviet troops invade Manchuria
August 14 Emperor Hirohito announces Japanese forces' unconditional surrender
August 15 VJ-Day; all offensive action against Japan comes to an end
August 17 Sukarno announces Indonesia independence
September 2 Japanese sign instrument of surrender in Tokyo Bay on the Battleship USS Missouri