Watch the bullying, both physical and rhetorical, committed by Donald Trump at the NATO summit, publicly insulting nations and people who have long been our allies. Compare that behavior to the deferential courting that he pays to tyrants in Saudi Arabia and Russia and elsewhere.

Think about the telephone call that Trump recently placed to Philippines President Rodrigo Duterte, the call in which our leader, the leader of the free world, the defender of democracy and the rule of law, personally congratulated Duterte for his anti-drug policy of shooting down thousands of people in the street, in cold blood, without regard to innocence or guilt.

Think about the message that sends to the rest of the world, and what it tells you about Trump's own world view.

Listen for the condemnation that must surely come from the Trump White House after the brutal beating of Kurdish Americans, right here on American soil, by thugs serving as bodyguards for Turkish President Recep Tayyip Erdogan. Listen, and you hear silence.

And watch while a congressional candidate in Montana physically assaults a reporter for politely asking a valid question about health care, and is then lauded for his assault by elements of the conservative movement.

Look at the budget perpetrated by the Trump administration, which defies the advice of top military leaders by stripping billions of dollars from the State Department and foreign aid programs and invests it all in guns and bullets and tanks. Look at the contempt that Trump has expressed for federal judges who dare to defy or question his edicts, and study the unconditional support expressed by Attorney General Jeff Sessions for police officers accused of brutality and unnecessary violence.

It's not quite accurate to identify Trump as the cause of all this, because in many ways he is its symptom. He did not produce these conditions; these conditions produced him. But it is certainly fair to point out that by his behavior, Trump validates the use of brute force and intimidation as means of solving complex problems. He has revealed himself as a man with neither the patience nor the intelligence to understand how complex things work, to learn what tools are available to him and how to use them. Instead, his solution to any problem is to take out a hammer and bang on it, as if that will make it operate better.

It won't. Brute force has its uses, but those uses are rare and come as a last option rather than a first option. When force and intimidation become the default approach to solving a whole range of challenges, as they have under this president, then something else is going on.

Again, look at what happened at the NATO summit. In his lecture to U.S. allies, Trump made it clear that he doesn't understand even basic issues about how NATO works. He attacked Germany for its trade policies, not understanding that as a member of the European Union, Germany has no one-on-one trade agreements with the United States. His attack also ignored the fact that Volkswagen, Mercedes and BMW have each opened major auto plants here in the United States, providing tens of thousands of jobs. BMW's plant in South Carolina is the company's second largest in the world, and it exports more vehicles to foreign markets than any other auto plant in the United States, foreign-owned or domestic.

If you're going to attack your friends in public, as Trump did, you should at least have your facts right, and Trump did not. His attempted projection of "strength" thus comes across as weakness, as a poor attempt to compensate for deficiencies elsewhere. And that's far from the only example of bluster as a bad cover for weakness.

In his comments at the summit, Trump also ostentatiously refused to commit himself to honoring Article Five of the NATO treaty. That pledge of mutual defense against outside attack has been the foundation of the alliance for 70 years. For 70 years, it has served as an effective deterrent first to Soviet aggression against European democracies and later to Russian aggression. Gary Cohn, Trump's top economic adviser, also told the press that Trump is undecided about maintaining sanctions that were levied on Russia after its invasion of Crimea and military intervention in Ukraine.

What does it do to a defensive alliance when its most powerful member injects doubt about its commitment? How can fellow NATO members have confidence in an American leader who was elected with Russian help, who repeatedly excuses or ignores Russian misbehavior, who welcomes Russian officials into the Oval Office after they have been accused of subverting U.S. democracy, and who tries to convey strength by picking on friends while he shrinks from confronting adversaries?