How did western democracies react to Nazi Germany taking over neighboring countries?

World War II is appropriately called “Hitler’s war.” Germany was so extraordinarily successful in the first two years that Hitler came close to realizing his aim of establishing hegemony in Europe. But his triumphs were not part of a strategic conception that secured victory in the long run. Nonetheless, the early successes were spectacular. After the defeat of Poland within a month, Hitler turned his attention westward. He believed that it was necessary to defeat Britain and France before he could again turn eastward to the territories that were to become the “living space” for his new empire. The attack on the Western Front began in the spring of 1940. Hitler took Denmark and Norway during the course of a few days in April, and on May 10 he attacked France, along with Luxembourg, Belgium, and The Netherlands. Once again his armies achieved lightning victories; Luxembourg, Belgium, and The Netherlands were overrun in a few days, and France capitulated on June 21. Only the British, now alone, obstructed Hitler’s path to total victory in the west.

The answer is monsoons.