World War I: The Battle of St Quentin Canal took place, which led to the British Fourth Army making the first breach of the German defensive Hindenburg Line.

World War I or the First World War, also known as the Great War, was a global conflict between two coalitions: the Allies and the Central Powers. Main areas of conflict included Europe and the Middle East, as well as parts of Africa and the Asia-Pacific. There were important developments in weaponry including tanks, aircraft, artillery, machine guns, and chemical weapons. One of the deadliest conflicts in history, it resulted in an estimated 30 million military casualties, plus another 8 million civilian deaths from war-related causes and genocide. The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic.

The Battle of St Quentin Canal was a pivotal battle of World War I that began on 29 September 1918 and involved British, Australian and American forces operating as part of the British Fourth Army under the overall command of General Sir Henry Rawlinson. Further north, part of the British Third Army also supported the attack. South of the Fourth Army's 19 km (12 mi) front, the French First Army launched a coordinated attack on a 9.5 km (6 mi) front. The objective was to break through one of the most heavily defended stretches of the German Siegfriedstellung, which in this sector used the St Quentin Canal as part of its defences. The assault achieved its objectives, resulting in the first full breach of the Hindenburg Line, in the face of heavy German resistance. In concert with other attacks of the Grand Offensive along the length of the line, Allied success convinced the German high command that there was little hope of an ultimate German victory.

The Fourth Army was a field army that formed part of the British Expeditionary Force during the First World War. The Fourth Army was formed on 5 February 1916 under the command of General Sir Henry Rawlinson to carry out the main British contribution to the Battle of the Somme.