In the epilogue of his new book about Britain’s decision to participate in the invasion of Iraq, Patrick Porter imagines the speech that Prime Minister Tony Blair might have given had he decided to not become involved. “Sometimes, there are worse things than war,” Porter has Blair say. “The threat [from Saddam] is years or decades distant.… We advise America to hold back, not to let terrorism provoke it into a reckless war” (pp. 224–26).

Instead, of course, Blair committed the United Kingdom to the war, making an early and only lightly conditional pledge of support to President George W. Bush. Porter’s account revisits the crucial period between September 2001 and March 2003, investigating the thinking in the three decision centers of Washington, D.C., London, and Baghdad. To do so, he draws on significant documentation that has recently become available: the testimony provided to Britain’s Chilcot Inquiry into the war’s origins, the voluminous diaries of Blair’s special adviser Alastair Campbell, and the remarkable recordings and transcripts of Saddam Hussein’s executive communications captured by US forces during the invasion.

Porter’s book comes in six parts. In the first, the existing explanations for the war are reviewed. In the second, he reconstructs the major decision points in the three capitals. Two chapters then explore the ideas that Porter believes drove Blair’s decision making: the propriety and efficacy of externally enforced regime change, the inherent dangers posed by rogue regimes, and his assumption that Britain’s influence over its US ally depended on a willingness to be there when the shooting started. The final sections reaffirm Porter’s view that Britain’s involvement in the war was a serious mistake and suggest that a more modest foreign policy, rooted in classical realism, can temper any future outbreaks of Blairite idealism.

Porter asks for the work to be considered along two dimensions. First, he hopes it will be read as diplomatic history, an exercise in empathy with and criticism of the decision makers who launched the war. Second, he asks that the work be regarded as a social-scientific explanation and suggests that he has offered an account of the causes of war superior to those in the extant literature (pp. 2–3).

I find Porter to have been very successful in his first aim. The work effectively reconstructs the arguments and considerations of the time as they played out in the minds—and the rhetoric—of the governments of the United States, the United Kingdom, and Iraq. Porter, who acknowledges the profound effect of the period on his own political thinking, has put together an engaging and comprehensive narrative. A particular strength is the effective use of the new documentation from Chilcot and the Saddam tapes and the resulting panoramic view of the war question.

The work is less successful in achieving its second goal of improving on existing attempts to explain Blair’s decisions. The problems begin in the introductory chapter, which stridently asserts the “inferiority” of existing work (p. 19). Although presented as a review of “a medium-sized academic literature” (p. 5), what follows is a mixing together of academic studies, exculpatory rhetoric from Blair and his defenders, arguments advanced by journalists, and opinions from a variety of editorial writers. This creates some difficulty in establishing the range and plausibility of existing scholarly explanations. For example, we are given a dismissal of the op-ed writers’ charge that Blair was Bush’s “poodle,” but not a consideration of the academic version of this argument: that Blair led the junior ally of a superpower and so had incentives to cooperate with the United States. Porter makes a strenuous effort to criticize the suggestion (which, in full disclosure, I have advanced in prior work) that Iraq was largely “Blair’s war,” and yet the majority of the book goes on to restate the central findings of that line of inquiry: that Blair was the principal agent and central decision maker, and it was his ideas, beliefs, and governing style that drove the process by which Britain committed itself to the US action.

Whatever the flaws may be in the existing arguments, I am not convinced that Porter has offered a superior explanatory framework. Although the book lacks an extended and systematic presentation of its hypotheses, Porter seems to work most often from an ideational frame, suggesting that “bad ideas … widely shared” (p. 1) caused Britain’s war choices. Thus, Porter argues, the war cannot be reduced to Blair’s decisions because its animating ideas—regime change, the threat of rogue states, and the necessity to be by the United States’ side in the conflict—circulated widely and were generally popular.

Ideational explanations for specific actions have to confront two important questions: Why are some ideas adopted by the relevant decision makers and not others, and how do these free-floating ideational configurations become enacted in government policy? In the Iraq case, once the actual decisions are reconstructed, the story inevitably becomes one with Blair at its center, as Porter acknowledges (p. 25). It is thus not clear what extra value the ideational argument offers beyond what has been established in the existing literature focused on Blair’s choices (e.g., John Kampfner, Blair’s Wars, 2004; Stephen Benedict Dyson, The Blair Identity: Leadership and Foreign Policy, 2009). One is also left with the puzzle of why, if the ideas that drove the war were widely shared and generally popular, Blair had to run “grave political risks to turn his Atlantic ambition into policy” and “warmakers” in the United States and the United Kingdom had to “persuade their countries to share their warlike idealism.” (p. 74). For those who remember, in February 2003, the largest parliamentary rebellion in 150 years and the largest political demonstration in British history, it is not clear that the ideas that underpinned the war commanded a wide consensus nor that they would have been adopted by any conceivable prime minister in Blair’s place.

It is unfortunate that this otherwise very compelling work has not advanced a tighter explanatory framework. Indeed, given the new evidence available to scholars of the conflict, an opportunity is missed here to systematically reconsider our priors about Blair’s choices. Rather than dismissing the existing literature out of hand, a more nuanced evaluation of what holds up and what must be reconsidered, given what we know now, would have served a greater social science purpose.

These qualms aside, when taken as a work of international history, Blunder is a welcome addition to the Iraq War corpus. Patrick Porter has produced a compelling, lively, and panoramic account of the war as a “hinge event” in British politics. It can be read by students at all levels and used with profit by academic researchers.