In the 1917 Labor split, Vaughan was expelled along with his brother, Premier Crawford Vaughan, and joined the new National Party.[3][4] Upon the defeat of the Vaughan ministry in July 1917, Vaughan did not nominate for a position in the new coalition ministry of Archibald Peake, and enlisted to serve in World War I.[5][6][7] He was controversially opposed at the 1918 election while away on active service, and being unable to campaign was defeated by Labor candidate Tom Gluyas.[8][9]