The three main Axis powers were Germany, Japan, and Italy. These countries worked as an alliance throughout most of World War II. Initially, Germany was the only country of the three to fight in what would become World War II, which began in 1939. Nearly one year later, Italy joined the fight with Germany against the Allies in 1940. Japan was the last of the three to join.
Other countries joined the Axis powers, but they contributed much less militarily. Among these countries were Hungary, Bulgaria, and Romania.
The Axis powers invaded many countries and controlled them throughout the war. Many of these countries were in Europe, though some were in the Pacific. Among them were Austria, Poland, Czechoslovakia, China, and many others. The Germans occupied other countries, such as Denmark, France, the Netherlands, and Belgium.
Working together, the Axis powers fought both in the Pacific and in Europe. In 1943, Italy surrendered to the Allied powers. In an unexpected turn of events, Italy decided to join the Allies shortly after their surrender to them.
Germany surrendered to the Allies in May of 1945. Japan surrendered in September of 1945, which was the official end of the war.