Ian F. W. Beckett & Keith Simpson 
Nation in Arms [PDF ebook] 
The British Army in the First World War

The Great War was the first conflict to draw men and women into uniform on a massive scale. From a small regular force of barely 250, 000, the British Army rapidly expanded into a national force of over five million. A Nation in Arms brings together original research into the impact of the war on the army as an institution, gives a revealing account of those who served in it and offers fascinating insights into its social history during one of the bloodiest wars.