Ambassador Burns and General Jones are the authors of the Atlantic Council's new report on "Restoring the Power and Purpose of the NATO alliance." Last week marked the 100th anniversary of the start of the Battle of the Somme in World War I, 141 days of carnage that killed or wounded over one million soldiers. This is a powerful reminder of a time fading from memory, yet not all that distant, that Europe was a war-torn continent. It's also a reminder of how fortunate we are that the United States and our allies changed that tragic arc of history at a crucial inflection point. We forged the rules-based international order out of the ashes of World War II. We are committed, ourselves, to human rights, democracy, rule of law, open markets, and peaceful settlements of disputes, and we built a NATO alliance to protect, defend, and advance a Europe whole, free, and at peace. Again we stand at a critical inflection point as the shadow of war is returned to Europe. The Atlantic Council report warns, "The peace, security, and democratic stability of Europe can no longer be taken for granted." Today, the NATO alliance faces the greatest threat to peace and security in Europe since the end of the Cold War. Indeed, the challenges to our alliance are great: radical Islamic terrorism radiating instability across the Middle East, the worst refugee crisis since World War II, a weakened European Union, and perhaps most significant of all, a revanchist and unrepentant Russia willing to use military force to achieve political objectives.