To the Editor:

I want to express my appreciation to Zbigniew Brzezinski for his generous review of my book War of Necessity, War of Choice: A Memoir of Two Iraq Wars (“A Tale of Two Wars,” May/June 2009). Praise from someone of Brzezinski’s stature is praise indeed.

I do, however, want to make sure that two matters central to the book are clear. The first concerns the Iraq war initiated in 2003. It is true that my opposition to this second Iraq war was not fundamental, largely because I assumed (along with virtually everyone else) that Iraq possessed at least some weapons of mass destruction. But even so, and as I note more than once in the book, I was “60/40” against the decision to go to war. (I go on to say that had I known then what is known now, that Iraq no longer possessed weapons of mass destruction, my stance would have been 90/10 against.) My position at the time (one expressed in many memos I wrote as director of the State Department’s policy planning staff) was one of skepticism about the need to go to war given all the United States and the Bush administration then had on their plate, all the likely problems a war would trigger, and the absence of a compelling answer to the question, Why now?

The second clarification involves just what is meant by “war of necessity” and “war of choice.” Wars of necessity are essentially unavoidable. They involve the most important national interests, a lack of promising alternatives to the use of force, and a certain and considerable price to be paid if the status quo is allowed to stand. Examples include World War II and the Korean War.

By contrast, wars of choice tend to involve interests that are less vital and the existence of viable alternative policies, be they diplomacy, inaction, or something else. The wars in Vietnam, Bosnia, and Kosovo (and the Spanish-American War a century before) were all wars of choice.

To be sure, there is unavoidable subjectivity in these characterizations. That said, the distinction between wars of necessity and wars of choice is not one between wars that are judged to have been good and wars that are judged to have been bad or between those seen as successes and those seen as failures. History’s judgment as to whether a war was worth fighting or fought well has no bearing on what kind of war it was. Thus, the first Iraq war, undertaken by President George H. W. Bush in 1991, would have remained a war of necessity even if it had proved to be far more costly or less successful. It just would have been a costly war of necessity. Similarly, the second Iraq war, initiated by George W. Bush just over a decade later, would have remained a war of choice even if the human and economic costs had proved to be more modest and the accomplishments greater. It just would have been a relatively inexpensive war of choice. Outcomes and the balance between results and costs shape our verdict of policies, but hindsight is not required to understand what was done and why.

Why does all this matter? When it comes to wars of necessity, it does not. By definition, such wars must be fought. But wars of choice place added burdens on decision-makers because of the often-considerable human, military, and economic costs associated with going to war. Such wars should be fought only after the most rigorous assessments of the likely costs and benefits of action -- as well as of the likely costs and benefits of implementing other policies. The right answer is not to rule out all wars of choice but to understand that they need to be rare so as to ensure that there is still the adequate will and ability to fight wars of necessity when they materialize.

President, Council on Foreign Relations