After Ted Cruz's withdrawal from the race, Donald Trump is the presumptive Republican nominee for president. This is real, it's happening, and it means Trump has a legitimate shot at becoming president.

That means it is time to start taking the possibility of a Trump presidency seriously — starting with his views on foreign affairs. As president, Trump would have near-total control over America's policy toward other countries, in a way he wouldn't with many domestic policy issues.

So it's worth special consideration: What would a Trump presidency foreign policy look like?

Some observers have tried to identify something like a Trump doctrine, a unifying set of beliefs that would govern his actions. But as best anyone can tell, there is no such thing. Even in his allegedly major foreign policy speech, his rhetoric constituted mostly vague, quasi-emotional platitudes — make America look strong, save our jobs, make the best deal — that don't add up to a strategic doctrine.

But while Trump may lack an ideology, he definitely has policy views on key issues such as Russia, China, and ISIS. Some are nationalist, some economic nationalist, some more dovish, and some defy categorization. Many of these ideas track with what he's said about foreign policy for years. Put together, they're an eclectic plan to take US policy and put it on a totally new course — often in some fairly radical, and fairly scary, ways.

Trump's plan for ISIS

On ISIS, Trump goes well beyond the hawkishness you hear from other Republicans, and beyond even his own plan to ban foreign Muslims from entering the United States. The most honest way to describe it is a platform of colonialism and institutionalizing war crimes.

His basic plan for ISIS is to cut off their oil funds, which is in fact in line with current US strategy, as is Trump's promise to accomplish this through bombing. But, more radically, he would also send in American oil companies to rebuild the infrastructure — and seize Syrian and Iraqi oil for the United States.

"They'll rebuild that sucker, brand new," Trump said. "And then I'll take the oil."

The US bombing campaign has already seriously depleted ISIS's oil profits, so the main change here would be to steal the oil for the US, which would be a direct return to old-school European colonialism. This seems bound to infuriate Middle Easterners and, indeed, much of the world.

It's difficult to specifically predict what would happen if the US installed oil-stealing engineers in the middle of the Syrian and Iraqi war zones. But it seems at least reasonably possible that this would unite the parties of those wars against the United States, potentially miring the US in both conflicts at tremendous military and diplomatic cost.

This is a longstanding Trump idea: Since at least 2007, he has advocated seizing Iraq's oil as compensation for America's losses during the Iraq War.

"In the old days, you know when you had a war, to the victor belong the spoils," Trump said in a 2011 interview. "You go in. You win the war and you take it. … You’re not stealing anything. … We’re taking back $1.5 trillion to reimburse ourselves."

Trump's terror plans would violate international and US law

Trump also promises to bring back waterboarding and techniques that he promises would be "much tougher" than that.

"Don’t kid yourself, folks. It works, okay? It works. Only a stupid person would say it doesn’t work," he said at a November campaign event. But "if it doesn’t work, they deserve it anyway, for what they’re doing."

He'd also target and kill the families of suspected ISIS fighters. "When you get these terrorists," Trump said in December, "you have to take out their families."

To be clear, both torture and the intentional killing of civilians are against international and American law. For Trump, this is surely part of the appeal.

"Donald Trump seems to have concluded that, by rejecting 'political correctness,' he is free to embrace war crimes," Max Boot, a prominent conservative foreign policy analyst, writes in Commentary.

Confusingly, Trump said in early March he would not order US military officers to disobey the law. But he subsequently suggested that he'd "like the law expanded" to permit torture.

Wage economic war on China and Mexico

Trump is deeply preoccupied with China and Mexico, both of which he sees as economic threats in a zero-sum competition with the US. On his website, two out of his five policy proposals (yes, only five) address those countries.

Trump believes China's cheap currency is hurting America's ability to export by making their goods artificially cheap, and that its loose intellectual property protections allow the theft of America's products. He has a multi-point plan for dealing with this:

Label China a "currency manipulator," which would entail putting tariffs on Chinese goods entering the US until they allow the renminbi to appreciate. Force China to stop taking US companies' property rights and undercut US businesses with lax labor and environmental regulations. His proposal does not specify how, exactly, he'd do that. Send more US military forces to the South China Sea, to show China we mean business. Lower the corporate tax rate to 15 percent, below China's current rate, to help US companies compete. Pay off the national debt to make sure "China cannot blackmail us with our own Treasury bonds."

What you see here is an overriding sense that what matters, most of all, is protecting American jobs and businesses — and that free trade, as currently constituted, works against America. There's no sense that America gains from trade with China (which it does, substantially); China is "just destroying us," as Trump says. The only appropriate response is to escalate and try to force China's acquiescence.

He feels similarly about Mexican immigration. "A nation that does not serve its own citizens is not a nation," Trump's policy website declares. "Any immigration plan must improve jobs, wages and security for all Americans."

Hence Trump's famous proposal to build a wall with Mexico, and make them pay for it. In Trump's eyes, Mexican immigration doesn't strengthen the US by bringing in new productive workers — it's a deliberate attempt by the Mexican government to dump off its worst citizens.

"For many years, Mexico’s leaders have been taking advantage of the United States by using illegal immigration to export the crime and poverty in their own country," the site says. "They have even published pamphlets on how to illegally immigrate to the United States."

Until Mexico builds the wall and pays for it, Trump proposes that the US impose some pretty harsh penalties on the Mexican government and Mexican nationals:

Impound all remittances (money sent home by immigrants) from undocumented Mexican workers. Slap a high fee on Mexican CEOs and diplomats looking to visit the United States — or even ban them altogether. Slap a separate fee on border crossing cards to make legal crossing expensive for Mexicans. Slap a third fee on NAFTA worker visas. Slap a fourth fee on entry to US ports from Mexico. If these measures don't force Mexico to pay for the wall, impose tariffs on Mexican goods and slash US foreign aid to Mexico.

In short: Pummel Mexican nationals and the Mexican economy until they give in to Trump's demands.

Make a deal with Vladimir Putin

For all of Trump's tough talk about terrorism, Mexico, and China, he's surprisingly dovish on another American enemy: Russia.

Trump sees its president, Vladimir Putin, as an admirable strongman who shares America's interest in destroying ISIS and could be a partner.

"I would talk to [Putin]," Trump said in a September GOP debate. "I would get along with him."

He expanded on his thinking in a recent interview with conservative radio host Michael Savage:

What’s wrong with having a good relationship with Russia? What’s wrong with Russia bombing the hell out of ISIS and these other crazies so we don’t have to spend a million dollars a bomb? Let them buy some of the bombs, ’cause that’s what’s happening.

Once again, you see Trump's peculiar instincts at play. He's worried about the economic cost of the ISIS war to the United States, not whether Russia actually shares America's priorities in destroying ISIS. Indeed, Russia's bombing campaign in Syria mostly targeted non-ISIS rebels, as its goal in Syria is propping up Syrian dictator Bashar al-Assad.

But Trump — author of The Art of the Deal — believes that through the power of personal charisma and dealmaking, he and Putin should be able to come to terms on Syria, Ukraine, and other issues of mutual concern.

Putin, for his part, has said that US-Russia relations would improve in a Trump presidency. As he put it in a December interview:

Trump is the absolute leader in the presidential race. He is a very outstanding person, talented, without any doubt. … He wants to move to another level of relations, a closer, deeper level of relations with Russia. How can we not welcome this? Of course we welcome this.

He has other dovish policies. On Syria, aggressive options like a no-fly zone are off the table.

"It's such a mess over there, with everybody involved, and the airspace is very limited," Trump said in October. "So are we going to start World War III over Syria?"

Keep the Iran deal in place and avoid toppling dictators

Donald Trump thinks the Iran deal is "terrible," as he put it in a July interview. "We're giving them billions of dollars in this deal, which we shouldn't have given them. We should have kept the money."

But unlike many Republicans, Trump will not promise to torpedo the Iran deal if elected. "I've heard a lot of people say, 'We're going to rip up the deal.' It's very tough to do when you say, 'Rip up a deal,'" Trump said in August. "The problem is by the time I got in there, they will have already received the $150 billion."

Instead, Trump says, he will enforce the Iran deal in the toughest possible manner, to stick Iran to the letter of the agreement (as is often the case with Trump, it's not obvious what this means in specific policy terms). "As bad as the contract is, I will be so tough on that contract," he says:

You know, I've taken over some bad contracts. I buy contracts where people screwed up and they have bad contracts. But I'm really good at looking at a contract and finding things within a contract that, even if they're bad, I would police that contract so tough that they don't have a chance.

This is consistent, ISIS policy aside, with Trump's approach to the Middle East more broadly. He often trumpets the fact that he opposed the Iraq War (though he falsely insists that he opposed it before it started). He has called the Middle East, writ large, "one big, fat quagmire" that the US should stay out of.

What this means, concretely, is that Trump will not launch wars to topple dictators, be they Bashar al-Assad or anyone else. As he explained at the November Republican debate:

So, I don't like Assad. Who's going to like Assad? But we have no idea who these people, and what they're going to be, and what they're going to represent. They may be far worse than Assad. Look at Libya. Look at Iraq. Look at the mess we have after spending $2 trillion dollars, thousands of lives, wounded warriors all over the place — we have nothing.

Here, again, Trump is positioning himself as a savvy negotiator carefully considering the bottom line, which in Iraq very clearly did come out against Americans' favor. He is promising to get Americans the best deal, whatever it takes.

The only thing you can say for sure about Trump's foreign policy is that it's unpredictable

But Trump's ostensible dovishness on Middle Eastern wars, and his claim to represent tough-nosed dealmaking, does not exactly square with his plan to send in oil companies to forcibly remove the region's natural resources.

Nor does it square with his suggestion that he would get China to make North Korean leader Kim Jong Un "disappear," which certainly sounds like an assassination threat.

These wild contradictions in Trump's apparent worldview, the policies that veer between radically realist and outright colonialist, are what make his foreign policy so difficult to read.

It's part of what makes him ultimately highly unpredictable: His decision-making and calculus is so all over the map that it's simply not possible to anticipate how he'd behave in office. And that unpredictability, perhaps more than anything else, is what makes the possibility of a Trump presidency so frightening.