[2] He studied at Trinity College Dublin, where he was elected a Scholar in 1986,[3] before completing his doctoral dissertation, Anglo-Prussian relations, 1804–1806: The Napoleonic Threat, at Peterhouse, Cambridge, under the supervision of Tim Blanning in 1993.
[4] In addition to his academic work, Simms also serves as the president[5] of the Henry Jackson Society, which advocates the view that supporting and promoting liberal democracy and liberal interventionism should be an integral part of Western foreign policy,[6] and as President of the Project for Democratic Union, a Munich-based student-organised think tank.
[7] He has advocated that the Eurozone should create a United States of Europe,[8] and also that this should continue the traditions of the Holy Roman Empire, appointing an elected Emperor.
[11] Evans described the book as a "one-sided picture", adding that even Simms has to acknowledge that there were periods of cooperation.
[12] British historian Richard J. Evans was critical of Hitler: Only the World Was Enough, arguing that the book makes a number of false claims, such as the claim that Hitler embraced socialism, and concluding that Simms "hasn’t written a biography in any meaningful sense of the word; he has written a tract that instrumentalises the past for present-day political purposes.