At Sigonella Naval Air Station in Italy, his last stop on his first foreign trip, President Trump declared the trip a “home run.” At best, it was a stand-up double. Even that’s a generous grade, given the point at which he begins. American diplomacy and international influence has reached its lowest point since 1914, because of eight years of former president Obama’s degradation of it.

As I wrote last week, the president’s speech to the assembled Sunni Muslim leaders was good but a long way from great. He labeled the ideology of radical Islam a “vile creed,” called upon them to rid their nations of terrorists, and mentioned Islamic terrorism using that term.

There was at least one big “you gotta be kidding me” moment when Trump announced the creation of a new “global center for combating extremist ideology,” which he said would include some of the Muslim nations present. Saudi Arabia, the nation in which Trump spoke, spends what must be tens of billions of dollars each year supporting madrassas — religious schools — around the world that teach Wahhabism, the official Saudi brand of radical Islam. Anyone who doesn’t know just how bloodthirsty Wahhabism is should read War in the Desert by John Bagot Glubb. (Hell, if you think you know all you need to know about Wahhabism, read it anyway. It gives a very prescient view into the “Nejed,” the country we now call Saudi Arabia.)

To believe that the Saudis will do anything other than continue to spread the poisons of Wahhabism or that the other Muslim leaders assembled for Trump’s speech would do anything different is delusional.

If Trump wanted to accomplish anything with that speech, he would have attempted to use American leverage to compel the audience to act. But he didn’t.

Islamic terrorism, as my friend Andy McCarthy reminds us, isn’t an offense committed against Islam. It is a part of Islam’s basic ideology. Mr. Trump didn’t begin to fight the ideological war that Islamic radicals have been fighting against us for decades. He won’t, because his national security adviser, Lt. Gen. H.R. McMaster, won’t let him. McMaster, one of Obama’s P.C. generals, insists there’s no connection between Islam and terrorism. In that and so much else, he’s willfully ignorant and comprehensively wrong.

Meanwhile, back in reality, DHS Secretary John Kelly told Fox News that if people saw the information about terrorism he sees every day, they’d “…never leave the house.”

Terrorism, Kelly added: “It’s everywhere. It’s constant. It’s nonstop. The good news for us in America is we have amazing people protecting us every day.… But it can happen here almost anytime.”

If the president wants to have any effect on the threat of terrorism, supported by the Muslim leaders he addressed, he needs to dedicate his presidency to the ideological war against Islam’s terrorist ideology — and governments that spread it such as Saudi Arabia’s — and fully engage in a defense of our way of life. Nothing less can have any effect. Firing McMaster would be an excellent first step, because McMaster will never permit him to engage in the ideological war that’s necessary to save our society.

In Israel, meeting Prime Minister Netanyahu, Trump both reaffirmed and undercut our alliance with the only Middle Eastern democracy. Before Trump arrived, he asked that the Israelis grant economic concessions to the Palestinians, apparently believing that would pave the way for Palestinian willingness to engage in another round of peace talks.

When Trump prayed at the Wailing Wall, the religious affirmation of Israel’s Judaism was a powerful message to the Palestinians. But what Trump giveth, Trump taketh away.

Palestinian President Mahmoud Abbas had reportedly told Trump that the Palestinians weren’t indoctrinating children to wage jihad against Israel or paying the surviving families of dead terrorists compensation for the terrorist’s absence. Those were perfect lies. Later, standing next to Abbas, Trump heard Abbas condemn the Manchester terrorist attack. The irony was almost too much to bear, given the fact that Abbas’s P.A. supports the al-Aqsa Martyrs’ Brigade, which commits acts of terrorism against Israelis almost daily (but not while someone like Trump is visiting).

The president wants to take on peace talks between the Palestinians and the Israelis. He can’t succeed for at least two reasons.

The U.N.’s resolutions creating Israel specify that it will be a Jewish state. The Palestinians will never agree to that. They insist on a “right to return” all Palestinians — not the number that left Israel when it was established but the six or seven million descendants of them — which would transform Israel into another Islamic dungeon.

The second reason is that Abbas, who was elected to a four-year term in 2005 that expired eight years ago, may soon be replaced by another radical, Omar Barghouti. Barghouti, as I document in my monograph The BDS War Against Israel, is a younger, smarter version of Abbas who will never make peace with the Jewish state on any terms. Abbas won’t sully his terrorist legacy by making peace on any terms the Israelis could possibly accept.

The president would do well not to invest much of his time and diplomatic capital in such a sure-to-lose exercise. He doesn’t have much of that capital to spend, but he may be able to gain more, if he continues to take a tough line on NATO spending and “climate change.”

In the Vatican meeting the Pope, the president presented him with speeches of Martin Luther King Jr. In return, he received a papal encyclical on global warming and endured, gracefully, a papal lecture on it.

In Brussels at NATO and in the G7 meeting in Sicily (same players as NATO, just a different setting), the president did pretty well if only by resisting the status quo.

Lecturing NATO on its members’ failure to invest in their own defense was a key element in Trump’s campaign. He did it again in Brussels, saying they weren’t paying what they should be paying. More importantly, he declined to join in the ritual commitment to NATO’s mutual defense promise. That, if nothing else, was a clear message. But it again fell on deaf ears.

Only five of NATO’s 28 members — America, the U.K., Poland, Estonia and Greece — meet the two percent of GDP defense spending goals set in 2006. Germany, the richest economy in Europe, spends only about 1.25 percent. It is among the most resistant to spending more. The promise Trump extracted from NATO, that its members would reach the two percent goal by about 2023, won’t be met.

NATO’s members should be convinced by Russia’s continuing aggression in Ukraine that they need to spend more. Even that hasn’t worked.

Trump’s refusal to re-commit to the mutual defense pledge in the NATO treaty should be a message to NATO’s contumacious members that they cannot rely on us to defend them unless they do more to defend themselves. But it won’t succeed.

NATO is still preoccupied with nonsense. The G7 meeting proved that. Trump was lectured repeatedly to endorse the Paris climate-change agreement, but he declined. If he rejects it, as he reportedly will, this week will send another message. It will take a war in which we decline to defend part of NATO to convince the members to increase their defense investments. We won’t allow that to happen. Even if we did, it would be too late for NATO to recover.

The president began restoring U.S. power and influence on this trip. His persistence will be the only measure of his success. He has a very long way to go.