Phony War
The Phony War (October 1939 - May 1940) was the period of World War II following the collapse of Poland until the German invasion of the Low Countries and France.
It was called "phony" because little land fighting took place, but in actuality it was part of a strategy devised by the British and French to win the war with as little bloodshed as possible. They were aware that they had fallen behind Germany in arms production, but that once underway, they could produce more and better armaments than Germany could. Additionally, as in World War I, Germany was vulnerable to a sea blockade. Along the land frontier, the French could defend safely behind the almost-impregnible Maginot Line. Within a few years, the German economy would collapse, and if resistance still continued, the better armed and equipped Allies could then launch an invasion.
Unfortunately for the Allies, the German U-boat fleet had improved, and took a significant toll on Allied shipping. German air power also increased decisively. In April 1940, the Germans launched a successful invasion of Norway, forcing the British and French into an embarrassing retreat. A month later, Germany launched a blitzkrieg assault through the Ardennes forest that led to the Fall of France. The "phony war" became real for millions of people.