The British Army First World War reserve brigades. At the start of the First World War British Army volunteers in the vast majority of cases joined their local infantry regiments reserve battalion. In 1916 when conscription was first introduced for the British Army, the existing regimental system could not cope with the large influx of recruits. By January 1916, when conscription was introduced, 2.6 million men had already volunteered for service, a further 2.3 million were conscripted before the end of the war; by the end of 1918, the army had reached its peak strength of four million men. To train the recruits from 1916 onwards twenty-six reserve brigades were raised, with an official complement of over 208,500 soldiers.