Why did American leaders work hard to secure multilateral approval from the United Nations or NATO for military interventions in Haiti, the Balkans, and Libya, while making only limited efforts to gain such approval for the 2003 Iraq War? In Reassuring the Reluctant Warriors, Stefano Recchia addresses this important question by drawing on declassified documents and about one hundred interviews with civilian and military leaders.

The most assertive, hawkish, and influential civilian leaders, he argues, tend to downplay the costs of intervention, and when confronted with...