Great Britain declared war on Germany on 4th August, 1914. Cricket and rugby competitions stopped almost immediately after the outbreak of the First World War. However, the Football League continued with the 1914-15 season. Most football players were professionals and were tied to clubs through one-year renewable contracts. Players could only join the armed forces if the clubs agreed to cancel their contracts. On 7th August, 1914, Lord Kitchener , the war minister, immediately began a recruiting campaign by calling for men aged between 19 and 30 to join the British Army. At first this was very successful with an average of 33,000 men joining every day. Three weeks later Kitchener raised the recruiting age to 35 and by the middle of September over 500,000 men had volunteered their services. Attendances at league games fell dramatically during the second-half of the 1914-15 season because of the impact of the First World War. It was decided that the Football League would not operate in the 1915-16 season. As football players only had contracts to play for one season at a time, they were now out of work. It has been estimated that around 2,000 of Britain's 5,000 professional footballers now joined the armed forces. Five former West Ham United players were killed in action during the war: Fred Griffiths, Arthur Stallard, William Jones, Frank Cannon and William Kennedy. West Ham's star forward, George Hilsdon, had to endure a mustard gas attack at Arras in 1917. This badly damaged his lungs and although he played briefly for Chatham Town after the war it brought an end to his professional football career. Fred Harrison was also badly gassed on the Western Front and never played football again. Another player, George Kay suffered from shellshock. Seven men registered with Newcastle United were killed: Richard McGough, Thomas Rowlandson, Thomas Cairns, James Fleming, Thomas Goodwill, Charles Randall and Thomas Hughes. Stan Hardy was gassed and was not able to play again. Stan Allan died of influenza soon after he arrived back from the trenches. Two Preston North End players, John Barbour and William Gerrish were killed on the Western Front during the war. Richard Bond was taken prisoner by the German Army and William Luke was so badly wounded his football career came to an end. Freddie Osborn, Preston's leading scorer in the 1913-14 and 1914-15 seasons, joined the 160th Brigade Royal Field Artillery (RFA). He served on the Western Front and in 1918 he was badly wounded by a bullet that hit him in the thigh. Major Frank Buckley kept a record of what happened to the men under his command in the Football Battalion. He later wrote that by the mid-1930s over 500 of the battalion's original 600 men were dead, having either been killed in action or dying from wounds suffered during the fighting. http://www.spartacus.schoolnet.co.uk/FWWfootball.htm
