In January 1941, Menzies flew to Britain to discuss the weakness of Singapore's defences. Arriving in London during The Blitz, Menzies was invited into Winston Churchill's British War Cabinet for the duration of his visit. 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. Unable to secure their support, and with an unworkable parliamentary majority, Menzies resigned as Prime Minister. The Coalition held office for another month, before the independents switched allegiance and John Curtin was sworn in Prime Minister. Eight weeks later, Japan attacked Pearl Harbor.