The Battle of Liège was the primary engagement in the German invasion of Belgium and the first battle of World War I. The attack on the city began on 5 August and lasted until 16 August, when the last fort was surrendered.
The German invasion led the British to declare war and the length of the siege may have delayed the German invasion of France by 4–5 days.
Railways needed by the German armies in eastern Belgium were closed during the early part of the siege and by the morning of 17 August, the German 1st, 2nd and 3rd armies were free to resume their advance to the French frontier, yet German troops only appeared in strength before Namur on 20 August.
The Belgian field army withdrew from the Gete towards Antwerp from 18–20 August and Brussels was captured unopposed on 20 August.
The siege of Liège had lasted for eleven days, rather than the two days anticipated by the Germans.

Belgian military operations in the east of the country had delayed German plans, which some writers claimed had been advantageous to the Franco-British forces in northern France and in Belgium.
Wolfgang Förster wrote that the German timetable of deployment had required its armies to reach a line from Thionville to Sedan and Mons by the 22nd day of mobilisation (23 August), which was achieved ahead of schedule.
In Bulletin Belge des Sciences Militaires, a four-day delay was claimed.
John Buchan wrote that "The triumph was moral – an advertisement to the world that the ancient faiths of country and duty could still nerve the arm for battle, and that the German idol, for all its splendour, had feet of clay".
In 2007, Foley called the neutralisation of the Belgian defences at Liège sufficient to enable the German right wing to squeeze through, a small bump in the road for the Germans, who had mobilised in two weeks and were ready to invade France by 20 August.
The Battle of Liège was the primary engagement in the German invasion of Belgium and the first battle of World War I. The attack on the city began on 5 August and lasted until 16 August, when the last fort was surrendered. The German invasion led the British to declare war and the length of the siege may have delayed the German invasion of France by 4–5 days. Railways needed by the German armies in eastern Belgium were closed during the early part of the siege and by the morning of 17 August, the German 1st, 2nd and 3rd armies were free to resume their advance to the French frontier, yet German troops only appeared in strength before Namur on 20 August. The Belgian field army withdrew from the Gete towards Antwerp from 18–20 August and Brussels was captured unopposed on 20 August. The siege of Liège had lasted for eleven days, rather than the two days anticipated by the Germans.
Belgian military operations in the east of the country had delayed German plans, which some writers claimed had been advantageous to the Franco-British forces in northern France and in Belgium. Wolfgang Förster wrote that the German timetable of deployment had required its armies to reach a line from Thionville to Sedan and Mons by the 22nd day of mobilisation (23 August), which was achieved ahead of schedule. In Bulletin Belge des Sciences Militaires, a four-day delay was claimed. John Buchan wrote that "The triumph was moral – an advertisement to the world that the ancient faiths of country and duty could still nerve the arm for battle, and that the German idol, for all its splendour, had feet of clay". In 2007, Foley called the neutralisation of the Belgian defences at Liège sufficient to enable the German right wing to squeeze through, a small bump in the road for the Germans, who had mobilised in two weeks and were ready to invade France by 20 August.
German invasion of Belgium