This history is important to remember at a time when the leader of the Western alliance seems determined to reduce it to a monetary transaction. During the Cold War, America had allies in unlikely places like Gdansk, Warsaw, Budapest, Vilnius, and Prague. These allies came through. The dissidents and workers didn’t contribute anything to military spending; at the time, their countries were in the Warsaw Pact, the other side, but their contribution to the common success was decisive, and equal to America’s own.

Donald Tusk went from being a dissident to being prime minister of Poland, and then to becoming president of the European Council—an institution of an undivided, democratic Europe. Poland went from being a poor, Soviet-occupied country to one that was relatively wealthy and free.

That good story—a miracle, actually—is replicated throughout Central Europe, and it is a testament to the success of what was then, and had been before, America’s grand strategy. America pursued, from President Woodrow Wilson through Presidents Franklin D. Roosevelt, Harry Truman, John F. Kennedy, and Reagan, a course reflecting the understanding that the advance of American interests was linked to the advance of American values.

America did not fight the Cold War for itself alone, but for the democratic world, the free world—and those who wished to join it. It did so not out of abstract charity, but because generations of Americans understood the linkage of interests and values. They also understood, through bad experience, that the failure of those values would lead to bad real-world outcomes, like the Second World War. The American grand strategy, developed the hard way through two world wars and executed after 1945, gave America and the rest of the West two generations of peace and unprecedented prosperity. First America helped Western Europe find peace, security, and prosperity. Then America and its partners helped extend that peace to almost all of Europe. And millions of people, Europeans and Americans, came out of this ahead.

Meanwhile, though, the world remains a dangerous place. Allies help America deal with those dangers.

America needed its allies after it was attacked on 9/11, and its allies came through. Soldiers from NATO and non-NATO countries—British, Canadian, French, German, Australian, Georgian, and many others—have fought in Afghanistan, in solidarity with us. Many have died doing so. The lives of 455 Britons, 158 Canadians, 86 French, and 54 Germans mean something to families who have given their loved ones in solidarity with America.

America may need them again. President Trump would do well to remember that.

On July 11, NATO leaders, including Trump, reached agreement on a Summit Declaration that affirms NATO solidarity and the rules-based international order, and urges efforts to thwart Russian aggression. It also calls on NATO allies to respect the alliance’s agreed goal of spending 2 percent of GDP on defense. It’s a good thing that this declaration was agreed on, and that the United States did not withhold or withdraw consensus (as the president did after the G7 Summit in June).