The North Atlantic Treaty Organization is the longest and most successful alliance still going today. But Donald Trump is looking to redefine that alliance in ways that would make it virtually meaningless.

Reuters:

In response to a question about potential Russian aggression towards the Baltic states, Trump told the newspaper in an interview that if Moscow attacked them, he would decide whether to come to their aid only after reviewing whether those nations "have fulfilled their obligations to us".

He added: "If they fulfill their obligations to us, the answer is yes."

Trump was quoted as saying he would force allies to shoulder defense costs that the United States has borne for decades, cancel longstanding treaties he views as unfavorable, and redefine what it means to be a partner of the United States.

"I would prefer to be able to continue" existing agreements, he said, but only if allies stopped taking advantage of what he called an era of American largess, the New York Times wrote.

Democratic presidential candidate Hillary Clinton's senior foreign policy adviser, Jake Sullivan, said in a statement: "Trump has apparently decided that America lacks the moral authority to advance our interests and values around the world."

David Corn, Washington bureau chief of the Mother Jones news website, said in a tweet that Trump's campaign manager Paul Manafort had told him the candidate had been misquoted.

Reuters was unsuccessful in attempts to reach Trump campaign staff for comment late on Wednesday.

Trump has for months raised questions about the money the United States pours into NATO, which he says needs to be reconfigured to take account of today's global threats.

His rhetoric has raised alarm in allied countries that still rely on the U.S. defense umbrella. The phrase "America First" was used in the 1930s by isolationists who sought to keep the United States out of World War Two.

There are two ways to measure what individual NATO members spend on the alliance; direct and indirect spending. As far as direct spending, Trump doesn't know what he's talking about. 

 In 2012, the Congressional Research Service produced a report that looked at direct funding in detail. Despite Trump’s claim that the United States is spending “billions and billions” on NATO, Defense Department budget documents show the annual direct contribution is under $500 million a year.

By this metric, Trump’s claims of the U.S. paying a disproportionate share, or “a lion’s share,” are wildly exaggerated.  The U.S. pays the most, but not significantly more than the next country — and the formula for calculating the different shares is reasonable.

But Trump approaches the truth when talking about indirect spending:

On the other hand, if Trump is talking about indirect spending on NATO, which exceeds direct funding, he begins to have a point. U.S. officials have long complained that other NATO members are not pulling their weight in the alliance; President Obama recently asserted to Atlantic Monthly’s Jeffrey Goldberg that some European allies are “free riders,” a term that Trump echoed in his CNN interview.

NATO documents show that a majority of NATO members fail to meet NATO’s guideline, established in 2006, that defense expenditures should amount to 2 percent of each country’s gross domestic product. The median spending in 2015 is just 1.18 percent of GDP, compared to 3.7 percent for the United States, NATO says. Just four other countries currently exceed the 2 percent guideline.

“The volume of the US defense expenditure effectively represents 73 per cent of the defense spending of the Alliance as a whole,” NATO says in a discussion of indirect funding. “This does not mean that the United States covers 73 per cent of the costs involved in the operational running of NATO as an organization, including its headquarters in Brussels and its subordinate military commands, but it does mean that there is an over-reliance by the Alliance as a whole on the United States for the provision of essential capabilities, including for instance, in regard to intelligence, surveillance and reconnaissance; air-to-air refueling; ballistic missile defense; and airborne electronic warfare.”

It's impossible to quantify exactly what the US spends on NATO largely because we are a global superpower with global responsibilites. Military assets earmarked for NATO can also be used elsewhere. 

But if you agree with Trump - that US assistance will depend on whether a nation has met its "obligation" to the US - you might as well break up the alliance now.  This may be Trump's ultimate goal, given much of his rhetoric about NATO.

That will be great news for Trump's friend Vladimir Putin who would then be able to dominate Europe in ways the old Soviet Union could only dream.