The inactive period ended with the surprise invasion (Apr. 9, 1940) of Denmark and Norway by the Germans. Denmark offered no resistance; Norway was conquered by June 9. On May 10, German forces overran Luxembourg and invaded the Netherlands and Belgium; on May 13 they outflanked the Maginot Line. Their armored columns raced to the English Channel and cut off Flanders, and Allied forces were evacuated from Dunkirk (May 26–June 4). General Weygand had replaced General Gamelin as supreme Allied commander, but was unable to stop the Allied debacle in the "battle of France." On June 22, France signed an armistice with Germany, followed by an armistice with Italy, which had entered the war on June 10. The Vichy government was set up in France under Marshal Pétain. Britain, the only remaining Allied power, resisted, under the inspiring leadership of Winston Churchill, the German attempt to bomb it into submission.
While Germany was receiving its first setback in the Battle of Britain, fought entirely in the air, the theater of war was widened by the Italian attack on the British in North Africa (see North Africa, campaigns in, by the Italian invasion (Oct. 28, 1940) of Greece, and by German submarine warfare in the Atlantic Ocean. Hungary, Romania, and Bulgaria joined the Axis late in 1940, but Yugoslavia resisted German pressure, and on Apr. 6, 1941, Germany launched attacks on Yugoslavia and Greece and won rapid victories. In May, Crete fell.
Great Britain gained a new ally on June 22, 1941, when Germany (joined by Italy, Romania, Hungary, Slovakia, and Finland), invaded the Soviet Union. By Dec., 1941, German mechanized divisions had destroyed a substantial part of the Soviet army and had overrun much of European Russia. However, the harsh Russian winter halted the German sweep, and the drive on Moscow was foiled by a Soviet counteroffensive.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.