A specialist in the history of pacificsm and Eastern Europe, Peter Brock studied at Exeter College, Oxford, where he came under the influence of pacifist ideas, particularly those of Bart de Ligt. During the Second World War, he declared as a conscientious objector and was briefly imprisoned before spending the remainder of the war on alternative service. After the war, Brock worked with a Quaker relief mission to Germany and Poland, sparking his interest in Eastern Europe. After the mission ended, Brock took graduate study at Jagiellonian University, receiving a doctorate in history in 1950. He earned a second doctorate at Oxford in 1954 and subsequently emigrated to Canada, where he taught at the University of Toronto from 1966 until his retirement.