World War II
World War II, or the Second World War (often abbreviated as WWII or WW2), was a global conflict lasting from 1939 to 1945, involving most of the world's nations
Participants in World War II
The participants in World War II were those nations who either participated directly in or were affected by any of the theaters or events of World War II....

—including all of the great power
Great power
A great power is a nation or state that has the ability to exert its influence on a global scale. Great powers characteristically possess military and economic strength and diplomatic and cultural influence which may cause small powers to consider the opinions of great powers before taking actions...

s—eventually forming two opposing military alliances: the Allies
Allies of World War II
The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

 and the Axis
Axis Powers
The Axis powers , also known as the Axis alliance, Axis nations, Axis countries, or just the Axis, was an alignment of great powers during the mid-20th century that fought World War II against the Allies. It began in 1936 with treaties of friendship between Germany and Italy and between Germany and...

. It was the most widespread war in history, with more than 100 million military personnel mobilised. In a state of "total war
Total war
Total war is a war in which a belligerent engages in the complete mobilization of fully available resources and population.In the mid-19th century, "total war" was identified by scholars as a separate class of warfare...

", the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing the distinction between civilian and military resources.

1936    World War II (Prelude to): In violation of the Locarno Pact and the Treaty of Versailles, Germany reoccupies the Rhineland.

1937    Chinese Air Force Day: The beginning of air-to-air combat of the Second Sino-Japanese War and World War II in general, when 6 Imperial Japanese Mitsubishi G3M bombers are shot down by the Nationalist Chinese Air Force while raiding Chinese air bases.

1939    World War II: Germany takes Memel from Lithuania.

1939    World War II: Italy invades Albania.

1939    World War II: Germany and Italy sign the Pact of Steel.

1939    World War II: Germany and the Soviet Union sign a non-aggression treaty, the Molotov-Ribbentrop Pact. In a secret addition to the pact, the Baltic states, Finland, Romania, and Poland are divided between the two nations.

1939    World War II: Nazi Germany invades Poland, beginning the war in Europe.

1939    World War II: following the start of the invasion of Poland the previous day, the Free City of Danzig (now Gdańsk, Poland) is annexed by Nazi Germany.

1939    World War II: France, the United Kingdom, New Zealand and Australia declare war on Germany after the invasion of Poland, forming the Allies.

1939    World War II: The Battle of Barking Creek.