Before his big foreign policy speech, Donald Trump let us know that “it won’t be the Trump Doctrine because in life you have to be flexible. You have to have flexibility. You have to change. You may say one thing, and then the following year you want to change it because circumstances are different.”

So we had the Monroe Doctrine, the Truman Doctrine, the Reagan Doctrine and the Bush Doctrine. But the Trump Doctrine is that doctrines are for losers.

On the center right, there are plenty of philosophies — realism, conservative internationalism and isolationism — to choose from. So which does Trump subscribe to? None and all, depending on the day he is speaking.

For example, Trump has announced some of the most ambitious goals in the Middle East of any presidential candidate in modern history. In his speech to the American Israel Public Affairs Committee (AIPAC), Trump promised that “we will totally dismantle Iran’s global terror network,” which he said had “seeded terror groups all over the world” and “perpetrated terror attacks in 25 different countries on five continents.” And Trump declared in no uncertain terms last week that the Islamic State “will be gone if I’m elected president. And they’ll be gone quickly. They will be gone very, very quickly.”

Even the most enthusiastic advocates of the Bush Doctrine would never suggest that the Islamic State could be eliminated “very, very quickly” — President George W. Bush described the battle against terrorism as “a generational struggle.” And the complete dismantlement of Iran’s terrorist infrastructure on five continents? Wow. Even the most ambitious neoconservatives have never gone that far.

Yet at the same time, Trump has also repeatedly said he plans to pull out of the Middle East so that he can save money and focus on nation-building here at home. “We are spending trillions of dollars in the Middle East, and the infrastructure of our country is disintegrating,” Trump has said, adding elsewhere that “We have to build our own country and that’s what we have to focus on.”

That sounds a lot more like President Obama, who declared that “over the last decade, we have spent a trillion dollars on war, at a time of rising debt and hard economic times. . . . It is time to focus on nation-building here at home.”

So which is it? Trump can’t dismantle Iran’s terror network and destroy the Islamic State while at the same time withdrawing from the Middle East so that he can spend the money on bridges and infrastructure.

Trump also contradicts himself when it comes to the ideological struggle with Islamist radicalism. In his speech last week, Trump correctly declared: “Containing the spread of radical Islam must be a major foreign policy goal of the United States and indeed the world. Events may require the use of military force, but it’s also a philosophical struggle, like our long struggle in the Cold War.”

That sounds a lot like the Bush Doctrine. “The war we fight today is more than a military conflict,” Bush told the American Legion in 2006. “It is the decisive ideological struggle of the 21st century.”

But Trump also declared in the same speech that our troubles in the Middle East “began with the dangerous idea that we could make Western democracies out of countries that had no experience or interest in becoming a Western democracy.” He has said that Syrian dictator Bashar al-Assad is someone with whom he could work (“I’ve been watching Assad,” he told Fox’s Bill O’Reilly, “and I’ve been pretty good at this stuff over the years, because deals are people. And I’m looking at Assad and saying, ‘Maybe he’s better than the kind of people that we’re supposed to be backing’ ”). Trump has also said that the world would be “100 percent” better with Saddam Hussein and Moammar Gaddafi in power, and that in Egypt “We should have backed [Hosni] Mubarak instead of dropping him like a dog.”

So Trump believes that (a) the war on terror is, like the Cold War, an ideological struggle between tyranny and freedom; and (b) that the way to win that ideological struggle is to support Middle Eastern tyrants as the alternative to Islamist radicalism? This isn’t realism; it is incoherent.

To complicate things further, Trump gave a name to his foreign policy non-doctrine: “America First,” he declared last week, “will be the major and overriding theme of my administration.” In the prepared text released by his campaign, the phrase “America First” was even capitalized.

But “America First” has been the rallying cry of American isolationists for 75 years, ever since Charles Lindbergh and the America First Committee lobbied against U.S. involvement in World War II in the 1940s. On “Fox News Sunday” this weekend, Trump embraced his inner Lindbergh. “We’re defending Germany, we’re defending Japan, South Korea, we’re defending Saudi Arabia,” Trump declared. “We’re the policeman to the world. And this country can’t afford to do it.”

In other words, Trump has managed to embrace isolationism, realism and internationalism — all at the same time.

Give him this much: That’s pretty flexible.

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