Donald Trump has been huffing and puffing about the need of America's NATO allies to spend the required 2.0 percent of gross domestic product on defense — and has suggested that as president he wouldn't honor the U.S. commitment to defend NATO allies under attack if that ally (or NATO countries generally, he's not always clear on these things) isn't living up to that commitment.

This is, in my view, extremely reckless and amounts to an invitation to Vladimir Putin's Russia to gobble up all or part of the Baltic states — NATO allies Estonia, Latvia and Lithuania — as it has gobbled up part of non-NATO ally Ukraine.

Who in NATO actually pays their required share? These figures from NATO provide the answers.

The estimates for 2015 are that the following countries will pay more than 2.0 percent of gdp: the United States (3.62), Greece (2.46), Poland (2.18), the United Kingdom (2.07), Estonia (2.04). Coming fairly close are France (1.80), Turkey (1.69), Norway (1.49).

These countries fall into different categories. The U.S., U.K. and France maintain significant out-of-area military capacities (though Britain used to have more). NATO allies Greece and Turkey have regarded each other as military threats for many years. Poland and Estonia are grimly aware of their former status as Soviet satellite and Soviet republic and do not want to return to that fate. Each has borders with Russia (Poland with Russia's Kaliningrad enclave), as does Norway (up near the Arctic Circle). The other two Baltic states, Latvia and Lithuania, spend considerably less on their militaries, but have made significant increases in 2014 and 2015.

Which nations are the laggards? Luxembourg (0.47), Hungary (0.85), Spain (0.89), Belgium (0.90), Italy (0.95), Slovenia (0.95), Czech Republic (0.97), and Canada (1.00). Germany, the largest European NATO member, is not far ahead (1.18).

Some of these nations have excuses. Luxembourg is a very tiny nation with a huge financial industry and therefore a very high gdp per capita. If it could build a military in proportion to its NATO commitment, it would be hard to wield. Hungary and the Czech Republic have recently had governments playing footsie with Russia — the opposite approach of Poland and Estonia. Slovenia is not very large.

But what are the excuses of Italy, with a population about the same as Britain or France? Or the excuses of Spain, with a population about the same as Poland? Or Canada, whose share of gdp spent on defense has been in decline and whose troops, according to a military historian I respect, were the best fighters on the Allied side in World War II? As for Belgium, it gets huge benefits from European institutions as the headquarters of NATO and the European Union, but doesn't seem to want to put much into the pot. Germany of course has historical reasons for holding back on military spending.

Trump risks destroying the NATO alliance and subjecting freedom-loving peoples to swinish Russian rule with his suggestion that he would ignore America's promise to defend a NATO ally against attack. And he seems oblivious to the fact that every recent administration has pressed NATO allies to spend more on defense.

This is Sisyphus's work, with our diplomats constantly trying to roll the stone uphill: something worth doing, but always frustrating. Putting a spotlight on NATO laggards may help, marginally. But suggesting the U.S. will fail to honor its commitments to NATO allies is horrifyingly irresponsible.

It is in America's interest to have a free, prosperous and peaceful Europe: we have seen alternatives which are hugely worse. Trump seems to think it's just a real estate deal, whose success is measured by how little money we put in and how much we get others to pony up. No.