This thoughtful and reflective book could serve as a guide for U.S. President Joe Biden’s national security team as they prepare for the challenges of the next few years. O’Hanlon draws on his experience of engaging in the big policy debates of the last three decades, including examining the preparation behind and the legacy of the United States’ recent wars. Taking into account the polarized nature of U.S. politics, he concludes that the United States must learn to limit its ambitions even while continuing to defend core interests. He advocates a strategy of “resolute restraint,” which means, for example, that if China attacks Taiwan, the United States should move quickly to help defend the island without believing that it has to then defeat China in a wider war. This is a valuable addition to current policy debates, on issues from climate change to nuclear arms control to the challenges posed by China and Russia.