Fighting with (and without) our allies

America’s strategic posture — both military and diplomatic — depends, in part, on our allies. What our allies can or cannot do — and will or will not do — is key to our ability to deter or defeat the many threats we face.

During the Cold War, America was a superpower. Because the free world looked to us for leadership and our adversaries respected us, we could influence every important world event. President Obama’s foreign policy ended all of that.

Winston Churchill once said: “There is only one thing worse than fighting with allies and that is fighting without them.” Mr. Trump is about to see just how bad it can be in both circumstances.

During the campaign, Mr. Trump criticized many of our allies, correctly saying that most of them aren’t spending enough on their own defenses. His harshest words were aimed at NATO, which he said is obsolete. Japan and South Korea, he said, might need nuclear weapons and that nations where U.S. troops were stationed should cover that cost.

And then there’s the United Nations, which isn’t an alliance at all. It’s a media circus used by dozens of despots to politically attack the few democracies left in the world. Mr. Trump can begin to repair our alliances and deal with the U.N., but none of it will be easy.

Most of NATO’s 28 members are essentially incapable of defending themselves. Despite their mutual defense pledge, only five of NATO’s members spend the agreed-to 2 percent of their gross domestic product on defense. Nearly all of its members are also members of the European Union, which competes with NATO for funding and on policy decisions.

Japan and South Korea invest significantly in defenses, the latter far more heavily. Pressured by its allies, Japan is about to increase its military budget significantly. They, and the Philippines, were cast adrift waiting for Mr. Obama’s illusory “Pacific shift.”

Mr. Trump will quickly come to realize that our national security — and that of our allies — is not just a matter of cash flow.

He needs to take a “tough love” approach toward NATO. Mr. Trump should tell its members that we can’t defend them unless they spend enough, and in the right way, for them to help us do so. They — and we — will be considerably stronger if they invest in their own defenses in a manner that best provides them the ability to operate with us, on and off the battlefield.

Israel is strong and wants to be faithful, but Mr. Obama sided with its enemies consistently in his Iran nuclear weapons deal and at the U.N. Mr. Trump can begin to repair the damage Mr. Obama has done to Israel. First, he needs to tear up Mr. Obama’s nuclear weapons deal with Iran, which endangers us as well as Israel, Europe and all non-Shiite Middle Eastern nations. Second, he should give a major speech in which he reaffirms our alliance with Israel in the strongest terms.

Mr. Trump and some of his advisers have already declared that they will defeat the poisonous Islamist ideology. Because most of the Arab nations of the Middle East and Southwest Asia help spread that ideology, they cannot be dependable allies, but they may join ad hoc coalitions of nations.

Least important, but sometimes most troublesome, is the U.N. If Mr. Trump applies any cost-benefit analysis to it, he’ll find that the U.N. costs a lot (around $8 billion a year) and delivers almost zero benefit. To deal with it, he can learn from Presidents Ronald Reagan and George W. Bush.

Mr. Bush seemed confused about the U.N. On one hand, his “Proliferation Security Initiative” — formed and operated independent of the U.N. — succeeded as an ad hoc alliance with nations ready to help interdict shipments of nuclear equipment and technology from North Korea. On the other hand, at NATO’s insistence, Mr. Bush spent six months trying unsuccessfully to get a U.N. blessing before invading Iraq.

Mr. Bush’s PSI followed the example of Reagan’s conservative internationalism by engaging the world without sinking in the U.N. quagmire. That is the model for ad hoc alliances that Mr. Trump should follow. At the same time, he should substantially reduce our funding of the U.N., thus showing that we have no tolerance for its anti-democracy antics.

The key to all of this is American leadership. By crafting an assertive foreign policy and backing it up with action, Mr. Trump can restore America to the superpower status it needs to recreate a Pax Americana.

• Jed Babbin served as a deputy undersecretary of defense in the George H. W. Bush administration. He is the best-selling author of books including “Inside the Asylum: How the UN and Old Europe are Worse than You Think” and “In the Words of Our Enemies.” He is a senior fellow of the London Center for Policy Research.