July: Japan invades North China from Manchuria.

July: the U.S. imposes trade sanctions, followed by an embargo, aimed at curbing Japan's military aggression in Asia. 

January: Adm. Yamamoto begins communicating with other Japanese officers about a possible attack on Pearl Harbor. 

Jan. 27: Joseph C. Grew, the U.S. ambassador to Japan, wires Washington that he has learned that Japan is planning a surprise attack on Pearl Harbor. No one in Washington believes the information. Most senior American military experts believe the Japanese would attack Manila in the Philippine Islands if war broke out. 

February: Adm. Husband E. Kimmel assumes command of the U.S. Pacific Fleet in Hawaii. Kimmel and Lt. Gen.Walter C. Short, commanding general of the Hawaiian Department, prepare for the defense of the islands. They ask their seniors in Washington for additional men and equipment to ensure a proper defense of military installations.

April: U.S. intelligence officers continue to monitor Japanese secret messages. In a program code-named Magic, U.S. intelligence uses a machine to decode Japan's diplomatic dispatches. Washington does not communicate all the available information to all commands, including Short and Kimmel in Hawaii. 

May: Japanese Adm. Nomura informs his superiors that he has learned Americans were reading his message traffic. No one in Tokyo believes the code could have been broken. The code is not changed. 

July: Throughout the summer, Adm. Yamamoto trains his forces and finalizes the planning of the attack on Pearl Harbor.

Sept. 24: The "bomb plot" message from Japanese naval intelligence to Japan's consul general in Honolulu requesting a grid of exact locations of ships in Pearl Harbor is deciphered. The information is not shared with Hawaii's Adm. Kimmel and Gen. Short.

November: Tokyo sends an experienced diplomat to Washington as a special envoy to assist Ambassador Kichisaburo Nomura, who continues to seek a diplomatic solution. 

Japan wants the U.S. to agree to its southern expansion in Asia diplomatically but if those efforts were unsuccessful, Japan was prepared to go to war. 

Nov. 16: Submarines, the first units involved in the attack, depart Japan.

Nov. 26: The main body, aircraft carriers, and escorts, begin the transit to Hawaii.

Nov. 27: Kimmel and Short receive a so-called "war warning" from Washington indicating a Japanese attack, possibly on an American target in the Pacific, is likely.