What was the “bulge” in the Battle of the Bulge?

The bulge was a break in the Allied lines caused by a German advance in the Ardennes forest in Luxembourg and Belgium, beginning on December 16, 1944.

The Germans advanced 50 miles on a 50-mile-long front.

On December 26, the Allies began to push the Germans back, and by the end of January 1945, the bulge in the lines had disappeared.