World War II
After Poland was defeated, the "Phoney War" began in Western Europe. British soldiers were sent to the Continent, but no large battles were fought between the two sides. Then, in April 1940, Germany decided to attack Norway and Denmark so that it would be safer to transport iron ore from Sweden. The British and the French sent an army to disrupt the German occupation, but had to leave when Germany invaded France. Neville Chamberlain was replaced by Winston Churchill as British prime minister in May 1940 because of the invasion.