At the outbreak of the First World War, the Coldstream Guards was among the first British regiments to arrive in France after Britain declared war on Germany. In the following battles, it suffered heavy losses, in two cases losing all of its officers. At the First Battle of Ypres, the 1st battalion was virtually annihilated: by 1 November down to 150 men and the Lt Quartermaster. The regiment fought at Mons, Loos, the Somme, Ginchy and in the 3rd Battle of Ypres. The regiment also formed the 4th (Pioneer) Battalion, which was disbanded after the war, in 1919. The 5th Reserve battalion never left Britain before it was disbanded.