Curtin took a seat on the newly created Advisory War Council in October 1940 and agreed to a plan by Menzies to travel to Washington and London. In January 1941, Menzies flew to Britain to discuss the weakness of Singapore's defences and sit with Winston Churchill's British War Cabinet. In Menzies's absence, Curtin co-operated with Deputy Prime Minister Arthur Fadden in preparing Australia for the expected Pacific War. Returning to Australia, with the threat of Japan imminent and with the Australian army suffering badly in the Greek and Crete campaigns, Menzies re-approached the Labor Party to form a War Cabinet. Menzies had planned a further trip to Britain to influence the conduct of the Allied campaign. Unable to secure Curtin's support, and with an unworkable parliamentary majority, Menzies resigned as Prime Minister. The UAP-Coalition held office for another month with Arthur Fadden of the Country Party as its leader, before the independents switched allegiance and John Curtin was sworn in as Prime Minister on 7 October 1941. Eight weeks later, Japan attacked Pearl Harbor.