World War II was won in 1945 by the main Allied powers, which consisted of the United States, Great Britain, China and the Soviet Union, that formed the primary alliance against the opposing Axis alliance.
World War II plays a key role in human history. The defeat of Nazi Germany resulted in an increased commitment to humanistic values, rule of law, morality and international convention. Although World War II spanned six years, in 1945 the Axis alliance suffered a devastating defeat. The Axis alliance consisted of Germany, Japan and Italy, with additional affiliate countries.
What Led to World War II?
World War II was the result of unresolved conflicts remaining from World War I (1914 to 1918) in addition to other causes, according to History.com. Tensions were still high in Germany because of economic conditions and the Treaty of Versailles terms, all of which contributed to the growth of the National Socialist (Nazi) Party, led by Adolf Hitler.
The Treaty of Versailles, signed in 1919, forced Germany to concede territories to Belgium, Czechoslovakia and Poland and required demilitarization and occupation of other European areas. It also asked that Germany accept full liability for initiating World War I and to limit its army of men and vessels, according to the Holocaust Encyclopedia.
Hitler quickly rose to power after becoming Reich Chancellor in 1933, convincing Germans that they were the world's superior race. Hitler began to secretly violate the Versailles Treaty by sending troops to occupy targeted countries, including Austria in 1938.
When World War II Began
Though it was a violation, Hitler invaded Poland on September 1, 1939 and two days later, France and Britain declared war, which officially began World War II. On September 17, Poland was invaded by Soviet troops, which quickly decimated the country. Germany and the Soviet Union were left to divide control over Poland by early 1940. The Soviet Union, then led by Joseph Stalin, began to invade the Baltic States and Finland. Soon after, Germany invaded Norway, Denmark, Belgium and the Netherlands, expanding a couple of months later into France. This began to pave the way for Germany to take over Britain through tactical air bombing. Britain's Royal Air Force defeated the German Air Force, which forced Hitler to postpone plans.
Hitler's Master Plan
In early 1941, the United States began to aid Britain, and Hitler began to implement the second phase of his plan, which was to exterminate Jews throughout German-occupied Europe to leave German Aryans as the master race. More than four million Jews would die in Polish death camps at the hands of the Nazis from 1941 through the end of the war.
Hitler hatched another plan in the summer of 1941 and ordered the invasion of the Soviet Union, but was overpowered by Soviet military weapons. Germany's second attempted invasion of the Soviet Union was stalled because of winter weather.
The U.S. Steps In
The U.S. entered World War II in December of 1941 when Pearl Harbor, a U.S. naval base in Hawaii, was attacked by Japan, killing thousands of U.S. troops. By December 8, the U.S., part of the Allied Powers, declared war on Japan, which was part of the opposing Axis Powers.
The End of World War II
By the summer of 1945, leaders from both sides, led by President Harry S. Truman, Winston Churchill and Stalin, agreed to work with the Japanese government to create the Potsdam Declaration. On September 2, 1945, World War II officially ended when Japan formally surrendered.