In world war 1 135 countries took place. The war exactly lasted for four yrs,3 months and 14 days. It was the first war to use mostly submarines, aeroplane, tanks or under water boars as weapons. In world war 2 When Hitler invaded Poland in September 1939, France and Britain declared war on Germany. After conquering Poland, Germany attacked France. France fell in June 1940, and soon the Nazis overran most of the rest of Europe and North Africa. Only Britain, led by Winston Churchill, was not defeated. World War1 -July 28, 1914- Austria-Hungary declared war on Serbia. World war 2-On one side were the Germany, Italy and Japan. On the other side were Britain, France, Australia, Canada, New Zealand, India, the Soviet Union, China and the United States of America.