The job of a film director is extremely challenging which requires the person to have knowledge of almost all the fields of film production. The success or failure of a film more or less depends on the capabilities of a film director.
On September 1, 1939, Hitler invaded Poland from the west; two days later, France and Britain declared war on Germany, beginning World War II. On September 17, Soviet troops invaded Poland from the east.
Others even regard World War I, which culminated in the Peace with the Central Powers in 1921 and World War II as parts of the same conflict, with only a breathing spell in between. War officially began on September 1, 1939, when Germany attacked Poland. Germany then crushed six countries in three months  Denmark, Norway, Belgium, Luxembourg, The Netherlands, and France  and proceeded to conquer Yugoslavia and Greece.