This commentary originally appeared on The Hill.

Four months ago, I warned that Republican nominee Donald Trump's statements about NATO revealed "a superficial and childlike understanding of the alliance." Trump's recent comments about NATO have demonstrated that I underestimated how much he would harm the alliance and thereby damage the security of the U.S. and our allies.

Trump's disclosure that if he is elected president, the U.S. may not defend NATO allies attacked by Russia, breaks over six decades of strong bipartisan support for the transatlantic alliance. Since World War II, every American president has recognized the importance of NATO to the U.S. and they would all reject the madness of Trump's views on the alliance. For example, Ronald Reagan described NATO as "the core of America's foreign policy and of America's own security." Trump fails to understand this central role of NATO in U.S. national security.



If elected president, Trump may accomplish what a hundred Soviet military divisions could not do throughout the Cold War: break NATO and end the successful alliance between the transatlantic democracies.

Whether he wins or loses, Trump has already pleased Russian President Vladimir Putin by harming the credibility of America as an ally and weakening deterrence in Europe. Trump has also refuted John Kennedy's pledge that "the American commitment to the freedom of Europe is reliable." In contrast, Trump promises that as president he is prepared to tell allies under attack, "Congratulations, you will be defending yourself."



NATO is an indispensable part of our national security. According to former Supreme Allied Commander Europe James Stavridis and Dov Seidman, pooled together, the members of NATO have a distinct military advantage: "3 million well-trained troops ... 24,000 military aircraft; 800 ocean-going warships; and close to a trillion dollars of combined defense spending." Without NATO, the U.S. will be a weaker nation. Trump's NATO policy will alienate allies and deprive the US of some of the most advanced military capabilities and strategic bases in the world. Without the support of our allies, the U.S. will be at greater peril and each American will pay more for less security.



Trump's willingness to abandon our allies makes new provocations by Putin more certain and future aggression by Russia more likely. By declaring that he would weaken America's commitment to NATO, Trump is jeopardizing one of the most important components of U.S. national security and is increasing the possibility of war in Europe. In doing so, Trump has now surpassed Putin as the most dangerous man in the world.



If this were not bad enough, Trump has also revealed that he is unfit to be in command of the U.S. nuclear arsenal. In an exchange with the media, Trump talked about responding to a terrorist attack by using nuclear weapons: "Somebody hits us within ISIS, you wouldn't fight back with a nuke?"



This is disturbing because nuclear weapons are not a proportional response to a terrorist attack and it does not make sense to use nuclear weapons against terrorists who are non-state actors. Trump may be willing to destroy thousands of Iraqi or Syrian civilians to kill a few ISIS terrorists, but the American public does not support such indiscriminate violence.



In a recent report, Trump repeatedly asked a foreign policy expert, "Why can't we use nuclear weapons?" The use of nuclear weapons may be the most dangerous and important decision an American president ever faces. Every president since Harry Truman has treated our nuclear arsenal with great caution and reluctance. Trump's question exposes a frivolous and unsafe attitude toward nuclear weapons and the catastrophic consequences of their use. This is another reason why Trump is the most dangerous man in the world.



In December, Trump gave us an important warning. "The biggest problem we have is nuclear ... having some maniac, having some madman go out and get a nuclear weapon." This election, every American voter has the power and duty to stop a dangerous man from destroying our alliances and gaining control of nuclear weapons.

