Donald Trump has threatened to leave NATO if he is re-elected president, raising concerns about both the security of Europe and the outcome of the war in Ukraine.

In fact, it is unlikely that Trump will decide to withdraw from NATO, former national security officials of the former president told Politico, but even if he does not formally withdraw from the organization, it does not mean that the US relationship with the NATO during Trump’s second term.

In exchange for continued US participation, Trump is expected to demand that European countries drastically increase their spending on NATO, which is his main complaint, but also a “radical reorientation” of NATO.

Reducing the role of the US in the security of Europe

According to Politico, Trump’s plan sees the US maintain its nuclear umbrella over Europe during his second term, maintaining its air power and bases in Germany, England and Turkey, as and their naval forces.

However, most of the infantry, armor, logistics, and artillery would likely pass from American to European hands.

The change lies in Trump’s intention to “significantly and substantially reduce America’s role in security — retreat, that is, to provide support only in times of crisis, rather than being the primary provider of combat power in Europe,” said Dan Caldwell, who he recently served as a senior adviser to Russell Vought, the former senior Trump administration official who in May was named policy director for the Republican National Convention and who is expected to play a senior role in a second Trump administration.

Another part of Trump’s plan calls for a two-tier NATO system, under which member states that have not yet met the goal of spending 2% of GDP on defense “will not enjoy the privilege of defense and guarantee of of the United States,” according to a national security expert.

This, however, could be seen as a violation of Article 5 of the treaty, which obliges each member to take “such measures as it deems necessary” to assist anyone under attack. However, members of Trump’s foreign policy staff note that the interpretation of Article 5 is flexible and does not require any member to respond with military force.

“Freeze” of NATO enlargement in the east

A swift resolution to the two-and-a-half-year conflict in Ukraine will likely fit into Trump’s plans for NATO. As part of a plan for Ukraine, Trump’s staff is considering a deal in which NATO would commit to not expanding further eastward, especially into Ukraine and Georgia, and negotiate with Russian President Vladimir Putin over the extent of Ukrainian of territory that Moscow can hold, according to two other Trump national security experts.

Taken together, Trump’s new approach in these areas would amount to an upheaval in NATO’s affairs that many critics say Europe is completely unable to deal with in the foreseeable future. The US is by far the largest supporter of NATO operations, spending around $860 billion on defense which represents 68% of total spending by NATO countries in 2023. The contribution is more than 10 times that of Germany, the second in country spending. A significant portion of that U.S. spending, amounting to about 3.5 percent of U.S. GDP, goes to the defense of Europe, though the Pentagon refuses to publicly disclose how much, says Jeremy Shapiro, director of research for the European Council on Foreign Relations.