That the British couldn't take Iraq without Soviet agreement is on the Soviets, surely. There was tension between the U.S. and Britain over extending the life of colonialism, resolved in favor of independence in not too many years. Not much revision in that. The struggles between democratic nations in the years between WWI and WWII over colonies are much more eye-opening; giving no evidence that democracies would hang together or defend anyone else's freedom. Yet indeed they did. We assume democracies will defend each other and feel they have a common interest. Pre-1939 almost no-one imagined that this was so.