Hundred Days Offensive Begins — Battle of Amiens

The Battle of Amiens—Erich Ludendorff's 'Black Day of the German Army'—opened the Hundred Days Offensive with 456 tanks and 10 Allied divisions advancing 15 km on the first day, the greatest advance on the Western Front in four years. German divisions collapsed and surrendered en masse. Haig's forces now employed combined-arms warfare—tanks, artillery, aircraft, and infantry coordinating effectively. The offensive continued until the Armistice and is considered the most sophisticated Allied military achievement of the war.