Sen. Rand Paul just gave one of the most important speeches on foreign policy since George W. Bush declared war on Iraq. But instead of declaring war on another country, Paul declared war on his own party. Or, at least, its entire approach to foreign policy.

In his address last night at the Center for the National Interest — a think tank founded by Richard Nixon — Paul gave, for the first time, a comprehensive picture of how he thinks about foreign policy. His moderate non-interventionism is a far cry from his father's absolutist desire for America to exit the world stage. But Paul's stance is light years away from the hyper-hawk neoconservatism that's dominated Republican foreign policy thinking for decades.

Paul is signaling that, when he runs for president in 2016, he isn't going to move toward the Republican foreign policy consensus; he's going to run at it, with a battering ram. If he wins, he could remake the Republican Party as we know it. But if he loses, this speech may well be the reason.

Paul tacks to Obama's right — but not the way you think

In the speech, Paul outlined four basic principles for conducting foreign policy.

First, "war is necessary when America is attacked or threatened, when vital American interests are attacked and threatened, and when we have exhausted all other measures short of war." But not otherwise.

Second, "Congress, the people's representative, must authorize the decision to intervene." No more war without express authorization.

Third, "peace and security require a commitment to diplomacy and leadership." That means expanding trade ties and diplomatic links around the world.

Fourth, "we are only as strong as our economy." For Paul, the national debt and slow growth are national security crises.

In the abstract, this doesn't tell you a whole lot about what Paul believes. But when he gives specific examples of where he agrees and disagrees with Obama's policy, the core idea becomes clearer: Paul wants to scale down American commitments to foreign wars.

the basic goal of the speech is to teach conservatives that they can oppose foreign wars and Democrats at the same time

Paul endorses the original decision to invade Afghanistan, but criticizes Obama's decision to escalate it. He savaged the Libya intervention, calling Libya today "a jihadist wonderland." He supports bombing ISIS, but blasted Obama's decision to arm the Syrian rebels: "the weapons are either indiscriminately given to 'less than moderate rebels' or simply taken from moderates by ISIS."

But Paul also, much more quietly, agrees with major parts of the Obama agenda. In a move that's bound to infuriate Republican hardliners, he's calling for negotiations with Iran over its nuclear program. He tacitly endorsed Obama's sanction-and-negotiate approach to the Ukraine crisis. And he called for a peaceful, cooperative relationship with China.

In Paul's ideal world, America only very rarely engages in war. Most of its relations with foreign powers are conducted via diplomacy and trade with other states. This is hardly a detailed theory of how to conduct American foreign policy, but it is absolutely a conservative vision for ramping down America's role in the world.

The Obama-bashing reveals Paul's real target: the GOP

Paul's agenda has a lot more in common with Barack Obama's view of the world than it does with, say, John McCain's. But his speech very cleverly played up the criticisms of Obama, and minimized the points of agreement. That's because the basic goal of the speech was to teach conservatives that they can oppose foreign wars and Democrats at the same time.

The real target of Paul's speech were the neoconservatives: the wing of the GOP that believes that American foreign policy should be about the aggressive use of American force and influence, be it against terrorist groups or Russia. Paul's unsubtle argument is that this view, dominant in the GOP, is a departure from what a conservative foreign policy ought to be.

His tactic for selling this argument is innovative. He's reframed arguments with neoconservatives as arguments with Obama, banking on the idea that he can get everyday Republicans to abandon hawkishness altogether if they see Obama as a hawk. "After the tragedies of Iraq and Libya, Americans are right to expect more from their country when we go to war," Paul said, clearly linking his critique of Obama to an attack on the Bush legacy.

Until this speech, Paul's 2016 foreign policy position hadn't been clear. Now it is. Rand "clearly wants a more restrained US foreign policy," says Dan McCarthy, the editor of The American Conservative magazine. According to McCarthy, who's talked about these issues with Paul's staff, Paul has been engaged in a "trial and error" experiment. The idea is to figure out how to make a less aggressive foreign policy politically viable in the Republican Party.

After this speech, the testing phase appears to be over. According to his advisors, this speech represents the final, overarching framework for Paul's worldview. Rand has developed a strategy for wrenching conservatives away from the Bush legacy, and it's now a question of implementing it.

The stakes in the Paul-GOP fight are tectonic

Paul is setting the terms of the 2016 election. So far, every plausible Republican nominee who's spoken about foreign policy has taken a more hawkish tack. Paul has picked a fight on foreign policy, and now he's going to get one.

The Republican primary, then, will be at least partly a referendum on the future of Republican foreign policy. If Paul wins the primary — let alone the presidency — then the GOP and its elected officials will have to line up behind him. That will mean defending his foreign policy against Democrats, who will likely blast Paul from an interventionist point of view.

"Paul's been clear about his goal," DNC Press Secretary Michael Czin told reporters before the speech. "He wants to see America retreat from our responsibilities around the world." A Paul primary win would force Republicans around the country to line up behind Paul's non-interventionism against these attacks. It might also lead the Democratic Party to become more hawkish as it unites against Paul's philosophies — and that's particularly true if Hillary Clinton, who is already on the more hawkish side of the Democratic spectrum, is the nominee.

"Rand is the first guy," McCarthy says, "to have a chance to come in and do something different than what our foreign policy has been doing in 70 or more years." He's not wrong.

Related: Zack Beauchamp explains 3 big reasons why there is less war today.