What is Mr. Trump’s complaint?
“NATO members must finally contribute their fair share and meet their financial obligations, for 23 of the 28 member nations are still not paying what they should be paying and what they’re supposed to be paying for their defense,” he said.
Yes and No. NATO has a budget to cover common civilian and military costs, and some NATO-owned assets are also commonly funded when they are used in operations. The United States pays 22 percent of those costs, according to a formula based on national income. None of the NATO allies are in arrears on these contributions.
Mr. Trump is referring imprecisely to a goal NATO has set for each member to spend at least 2 percent of its gross domestic product on its own defense each year. He is correct that only five of the 28 members currently meet that goal, and they are the United States, Greece, Britain, Estonia and Poland.
Are NATO members violating a rule?
No. The 2 percent standard is just a guideline, not a legally binding requirement. In 2006, even as the United States was increasing military spending because of the wars in Afghanistan and Iraq, European allies were shrinking their military spending. NATO defense ministers that year adopted a guideline suggesting that each spend the equivalent of 2 percent of its annual economic output on its military — but it was a target, not a rule, and not endorsed by heads of state.
Only in 2014, after Russia annexed Crimea and intervened militarily in eastern Ukraine, did NATO leaders meeting in Wales agree to the 2 percent standard, and even then they urged members to “move toward” that goal by 2024, still seven years away.
Do NATO allies owe the United States money?
“Many of these nations owe massive amounts of money from past years and not paying in those past years,” Mr. Trump said.
No. This is not a matter of members failing to pay dues. The allies arguably may have less capable militaries than they should have, but none of them owe anyone anything. “Europe may owe itself; it certainly owes nothing to the U.S.,” said Ivo Daalder, a former ambassador to NATO under Mr. Obama.