The Isle of Man TT was first cancelled because of war in 1915, after the 1914 event became the last TT held before the First World War. Racing did not return until 1920.
The interruption covered the years 1915 through 1919. The war transformed the Isle of Man and Britain’s priorities, diverting people, transport, machinery and resources away from international motorcycle racing. The TT’s public-road course could not continue operating as it had during peacetime.
The 1914 TT itself had taken place in May and included Junior and Senior races. When competition resumed on 15 June 1920, it was the first post-war TT and introduced a new Lightweight class for 250cc machines. The wording can cause confusion because 1914 was the last year racing took place, while 1915 was the first year with no TT. The Second World War caused another suspension, from 1940 to 1946.