Why does the United States need European allies, and why is it getting more difficult for those allies to partner with Washington in standing up to China, pushing back against Russia, and pursuing other common interests around the world? This book addresses the economic, demographic, political, and military trends that are fundamentally upending the ability and willingness of European allies to work with Washington. Brexit and its impact on Britain's economy and its military, Germany's seemingly relentless economic and political rise, France's continuing economic malaise, Italy's aging population and its withdrawal from major overseas operations, and Poland's demographic decline and single-minded obsession with Russia will combine to make partnership with Washington nearly impossible. In short, the constellation of allies and partners the United States has relied on since 9/11 will look very different a decade from now. How should Washington respond? It doesn't hold all the cards, but this book offers an array of practical recommendations for American leaders. By leveraging these proposals, U.S. policy-makers can avoid the worst-case scenarios and make the most of limited opportunities.