He founded the Reform Party which campaigned for freehold tenure and free enterprise. As Prime Minister (1912–25) Massey also made extensive purchases of remaining Maori land. He was challenged by militant unionists (Red Feds) and broke the strikes of 1912–13, having enrolled farmers as special constables—‘Massey’s Cossacks’. He committed New Zealand manpower heavily in World War I, but his hold on domestic politics weakened with increasing urbanization.