This site, which is maintained by enthusiast Michael Duffy, provides an excellent introduction to the history of the First World War 1914-1918. It includes a timeline of key events, biographies of leading figures, accounts of major battles such as the Somme and Passchendaele, descriptions of trench warfare and the use of poison gas. A particular strength of the site are the sections containing full-text treaties, photographs, archive recordings of songs and images of propaganda posters. http://www.firstworldwar.com/