The 1940's By megan_luvs_christ Period: Jan 1, 1940 to Dec 31, 1949 1940's Apr 20, 1940 Nazi Germany invades Norway, Denmark, Holland, Belgium, and Luxembourg. Apr 20, 1940 The world's first helicopter takes flight. Apr 20, 1940 Winston Churchill becomes Prime Minister of Great Britain. Apr 20, 1941 German warship Bismark sunk.