Asquith's British coalition government of 1915 came about in the aftermath of the Gallipoli disaster, when it was felt it was necessary to bring the Conservatives into the government to shore it up. The Conservatives were not terribly pleased with the offices they received in this new government, however, and Tory leader Andrew Bonar Law became increasingly less impressed with Asquith and the Liberals' conduct of affairs. The government collapsed as a result of the resignation of the Conservatives, who refused to serve any longer under Asquith. Asquith and most of the Liberals then moved into opposition, while the Conservatives formed a new coalition with a minority of the Liberals, under the leadership of Liberal David Lloyd George.

Source: Butler, David and Gareth Butler. Twentieth Century British Political Facts, 1900-2000. (St. Martin's, 2000)