Billy Hughes increasingly dominant in public affairs with the rise of Fascism in Europe and militant Japan in Asia. From 1938, Prime Minister Joseph Lyons had Hughes head a recruitment drive for the Australian Defence Force. On 7 April 1939, Lyons died in office. The United Australia Party selected Robert Menzies as his successor to lead a minority government on the eve of World War Two. Australia entered the Second World War on 3 September 1939 and a special War Cabinet was created after war was declared – initially composed of Prime Minister Menzies and five senior ministers including Hughes. Labor opposition
Prime Minister of Australia becomes acting Prime Minister in those circumstances. Three Prime Ministers have died in office – Joseph Lyons (1939), John Curtin (1945) and Harold Holt (1967). In each of these cases, the Deputy Prime Minister (an unofficial office at the time) became an interim Prime Minister, pending an election of a new leader of the government party. In none of these cases was the interim Prime Minister successful at the subsequent election. As of , there are seven living former Australian Prime Ministers. The greatest number of living former Prime Ministers at any one time was eight. This has occurred twice: