The formation of the Southern Railway was rooted in the outbreak of the First World War, when all British railway companies were taken into government control. Many members of staff joined the armed forces and it was not possible to build and maintain equipment at peacetime levels. After the war. the government considered permanent nationalisation. but instead decided on a compulsory amalgamation of the railways into four large groups through the 1921 Railways Act, known as the Grouping. The resultant amalgamation of the four south coast railways to form the Southern Railway meant that several duplicate routes and management structures were inherited. The LSWR had most influence on the new company, although genuine attempts were made to integrate the services and staff after 1923. The rationalisation of the system led to the downgrading of some routes in favour of more direct lines to the channel ports, and the creation of a co-ordinated, but not necessarily centralised form of management, based at the former LSWR headquarters in Waterloo station.