When ? did it start
It all started on 3rd September 1939 - 4th September 1945.
So it lasted for 6years and 1 day.

Who ? Was on each side
Britain fought with many other countries. World War 2 involved 61 countries with 1.7 billion people ( three quarts of the whole wide worlds population.

Where ? did it happen
It happen all over the world that's why its called "world" war 2.

Why ? did it happen
Because in 1933