This timeline of events preceding World War II covers the events (mostly during the interwar period [1918–1939] after World War I) that affected or led to World War II.
1910s: 1910 · 1918 · 1919
1920s: 1920 · 1921 · 1922 · 1923 · 1924 · 1925 · 1926 · 1927 · 1928 · 1929
1930s: 1930 · 1931 · 1932 · 1933 · 1934 · 1935 · 1936 · 1937 · 1938 · 1939
Leaders of major participating countries
October 8
September 5
August 22–29
October 28–31
October 28
November 11
November 13
December 27
January 4–15
January 18
January 31
February
February 13
March 2
March 12
March 21
May 15
June 21
June 28
July
August 1
August 3
August 8
September 10
September 12
November 27
January 21
February 24
March
June 4
August 10
October
November 2
November 15
December 24
Spring
March 7–17
March 18
April 24
August 25
August 29
October 5
November 9
February 6
March
April 16
October
October 11
October 29
November 1
January 11
January 26
June
July 24
August 31
September 27
October 23–25
October 29
November 8
January 21
February 1
March 16
April 1
April 6
June 10
August 16
August 18
January 20
April 4
May 12
July 18
December 1
January 3
January 31
April 24
September 8
December 25
April 12
May 20
June 7
November 12
December 14
May 3
May 28
June 4
August 2
August 27
October 1
November 6
February 9
February 11
March 28
April 3
June 7
July 24
August 31
October 29
April 22
June 30
September 14
May 19
September 18
September 19
January 7
January 28
February 27
March 1
April 10
May 4
May 30
July 25
August 30
November 4
November 8
November 21
December 3
January 1
January 30
February 27
February 28
March 4
March 20
March 23
March 24
March 27
April 1
April 26
May 1
May 2
May 15
May 31
June 21
July 14
August 25
September 2
September 12
October 19
November 16
November 24
January 26
February 9
February 12–16
March 20
May 5
June 30
July 20
July 25
August 2
August 8
September
October 5
October 9
October 16
December 1
December 5
December 29
January 7
June 18
August 31
September 15
October 3
November 14
January 20
February 6
February 26
March 7
March 25
May 5
June 3
July 18
August 1
August 19
October
October 18
November 3
November 14
November 15
November 25
December 1
December 12
December 23
December 24
January 20
February 21
26 April
May 7
May 28
June 21
July 7
August 8
August 13
October 5
October 13
November 5
November 6
November 26
December 1
December 8
December 11
December 12
December 13
January 26
March 6
March 13
March 24
July 6–16
July 29
August
September 27
September 30
October 5
November 7
November 9
January 25
January 27
March 14
March 15
March 20
March 21
March 23
March 25
March 31
April 1
April 3
April 4
April 7–12
April 14
April 18
April 28
April 29
May 11
May 17
May 22
May 31
June 7
June 14
July 10
August 2
August 23
August 25
August 28
August 30
September 1
Americans think of WW2 in Asia as having begun with Pearl Harbor, the British with the fall of Singapore, and so forth. The Chinese would correct this by identifying the Marco Polo Bridge incident as the start, or the Japanese seizure of Manchuria earlier. It really began in 1895 with Japan's assassination of Korea's Queen Min, and invasion of Korea, resulting in its absorption into Japan, followed quickly by Japan's seizure of southern Manchuria, etc. - establishing that Japan was at war from 1895-1945. Prior to 1895, Japan had only briefly invaded Korea during the Shogunate, long before the Meiji Restoration, and the invasion failed.
...on 26 January 1934 Poland and Germany signed their own ten-year non-aggression agreement.
Because these exercises had been in progress since June 6...
British and French efforts to avoid another European war quickly disintegrated, and on 31 March Poland secured agreements with both countries for their military intervention should Germany invade.
On 29 April Hitler ominously renounces Germany's non-aggression pact with Poland.