One way to understand the difference between Donald Trump and Hillary Clinton is to distill the world to its essence: people, land, and ocean. The United States has a lot of people and a lot of land, good relations with the people in the lands to its north and south, and oceans to its east and west. As Anders Fogh Rasmussen puts it, America is bordered by “two friendly neighbors and fish.” As a result of this geographic position, Rasmussen argues, Americans have the luxury of alternating between what you might call Trumpian and Clintonian views of the wider world.

“When it comes to the global village, the United States is a big, rich house with a wall and a moat around it,” the former NATO secretary-general and Danish prime minister writes in his new book, The Will to Lead, whereas other powerful countries live in more dangerous neighborhoods. “Throughout history, that privileged position has allowed America to swing between two opposing roles. At times, the United States has acted as the world’s policeman, the one that keeps order in the village and makes sure everyone else sticks to the rules. At other times, it has preferred to be its own gatekeeper, ignoring what was going on in the street outside unless it impacted directly on American security.”

Donald Trump wants the United States to be a full-time gatekeeper, which puts the Republican nominee for president at odds not just with rival Hillary Clinton, but also with his own running mate Mike Pence and many leaders of the Republican Party. This divide was evident during the second presidential debate on Sunday, when Trump sharply criticized Pence for advocating that the U.S. bomb the Syrian military if Russia and the Assad regime continued to strike civilians in the city of Aleppo. Clinton had just called for a no-fly zone in Syria in response to Russian aggression. Pence and Clinton, in other words, want America to police violations of the international rules of warfare. Trump, by contrast, is willing to ignore those violations if it means defeating ISIS. “I don’t like Assad at all,” the Republican candidate said at the debate. “But Assad is killing ISIS. Russia is killing ISIS.” Assad and Russia may be committing war crimes, but, in Trump’s view, they’re keeping the barbarians from America’s gate.

Trump, in fact, has explicitly rejected the notion that the United States should be “the world’s policeman.” Yet so have Bernie Sanders, Barack Obama, George W. Bush, and George H.W. Bush. It’s a bipartisan platitude, intended to signal that America can’t possibly solve every problem everywhere. Trump, however, goes much further. He isn’t just saying that the U.S. can’t police the world on its own. Ironically for a man who presents himself as the law-and-order candidate, he’s suggesting that the United States doesn’t even need to be involved in enforcing international law and order as it’s presently defined. More than any previous major-party presidential candidate, Trump has questioned the value to America of the U.S.-led international system that Harry Truman helped design after World War II: NATO, free trade, nuclear nonproliferation, mutual-defense treaties and overseas military bases, and so on.

Clinton celebrates this system. “Are we going to lead the world with strength and in accordance with our values?” she asked during the first presidential debate. “That’s what I intend to do. I intend to be a leader of our country that people can count on, both here at home and around the world, to make decisions that will further peace and prosperity, but also stand up to bullies, whether they’re abroad or at home.”

Trump position couldn’t be further from Clinton’s. The United States, he argues, shouldn’t lead the world with strength until it’s stronger at home. It shouldn’t preach its values when those values have been tarnished by domestic problems. Allies who “count on” America are really moochers who are draining the country of its wealth. The idea that U.S. leadership advances global “peace and prosperity”—the conventional wisdom in Washington that it’s a win-win for America as well as the world—is a sham; international affairs is a zero-sum, every-country-for-itself struggle between winners and losers, and the U.S. is currently losing while its so-called allies and whip-smart adversaries win. America, in Trump’s words, is a “big stupid bully ... systematically ripped off by everybody.”

Rasmussen says he’s not interested in picking sides in the U.S. election, but his preferences are obvious. “If Mr. Trump were to be elected president of the United States, I am concerned it would be the end of the American-led world order,” he told Politico in August. In The Will to Lead, Rasmussen makes a detailed case for why the unraveling of that order would be a bad thing for both the United States and the world.

Rasmussen, who was leading NATO in 2014 when Vladimir Putin intervened militarily in Ukraine and annexed Crimea, is particularly troubled by Trump’s admiration of the Russian president and refusal to criticize Russian aggression. He’s also concerned by Trump’s musings about not defending NATO members if those members haven’t fulfilled their financial obligations to the military alliance. “If a NATO ally was attacked by Russia, and if the alliance did not respond to that, the alliance is finished,” Rasmussen said.

Trump “has praised President Putin and other autocrats in a way that leaves me with the impression that he would rather conduct domestic policies and nation-building at home, so to speak, while the world could live without American engagement,” Rasmussen told me. “And that’s not how the modern world functions.”

Rasmussen’s book plays on the political trope that America cannot be the policeman of the world; he asserts that America—with its unrivaled military, economic, and diplomatic power—must play precisely that role. “The U.S. is destined to lead whether you like it or not,” he said. “As the world’s only superpower, that’s your burden.” The United Nations and European Union are too weak and internally divided to assume this responsibility, Rasmussen added; China, as a communist dictatorship, lacks the credibility that democracies possess, while Russia, as a depleted, distrusted power, lacks the capabilities to police the world.

Rasmussen claims that America’s role as the world’s policeman was in doubt well before the 2016 election. Barack Obama has demonstrated a degree of Trump-like “isolationism,” he argues, with grim consequences. “Experience shows that when the United States retreats or retrenches, it will leave behind a security vacuum, and that vacuum will be filled by the bad guys. And that’s what we are seeing,” he said. “While America and Europe slept, President Putin attacked Ukraine and he launched a reckless military operation in Syria.”

As Americans learned during the Pearl Harbor and 9/11 attacks, he continued, “It is in America’s interest to strike enemies on their soil instead of waiting and seeing them hit you on your soil.” Preventing conflicts or resolving them when they’re minor is less expensive than trying to treat them when they’ve grown unmanageable, he said, citing the price of U.S. inaction during the early stages of the Syrian Civil War. The cost to the United States of, say, stationing troops overseas or providing the bulk of NATO’s resources are more visible than the value America derives from those actions. But the value, according to Rasmussen, is immense: an “unprecedented era of peace and prosperity,” and 70 years without nuclear war or world war. Most Americans, moreover, benefit economically when “free trade and exchange between peoples around the world take place peacefully and according to certain rules.”

“American ships sail the world’s seas, American tourists travel the world’s countries, American companies invest in the world’s industries, American consumers buy the world’s goods, and the ‘Made in the USA’ label is in high demand across the globe,” Rasmussen writes in The Will to Lead. “All of that has been made possible by the rule of international law.” America designed this system, he notes, and it “stands to lose the most if it is overthrown.”

Rasmussen acknowledges that other countries, and especially other like-minded democracies, need to expend more resources to help the United States carry out its “sheriff duties.” He says Trump’s criticism that America’s fellow NATO members should be spending a greater percentage of their GDP on defense is “absolutely” fair, though he notes that European defense spending has increased over the last year as it’s become clear to European leaders that Russia is less a “partner” than an “adversary” intent on restoring “Russian dominance in former Soviet territory.”

But Rasmussen overlooks other weaknesses in his argument. He suggests, for example, that Obama’s reluctance to play the role of global policeman enabled Russian aggression in Ukraine, but Russia also attacked Georgia in 2008, when George W. Bush—a president Rasmussen believes took U.S. leadership seriously—was in office. He argues that the violence and volatility that followed the Iraq War, which he supported as the Danish prime minister, and the Libya intervention, which he helped lead as NATO secretary-general, resulted from lackluster “political follow-up” after successful military operations, without considering the possibility that the wars represent not poorly executed missions, but a failed, overly militarized model of policing in need of radical reinvention.

Rasmussen, moreover, claims that American leadership is necessary “because the world is on fire,” from Raqqa to Crimea to the South China Sea. But it’s not clear that the world is actually on fire. As the psychologist Steven Pinker and the Colombian President Juan Manuel Santos recently wrote, the “world’s wars are now concentrated almost exclusively in a zone stretching from Nigeria to Pakistan, an area containing only a sixth of the world’s population. Far from being a ‘world at war,’ as many people believe, we inhabit a world where five out of six people live in regions largely or entirely free of armed conflict.”

If nothing else, however, the urgency with which Rasmussen is making his case—he says he sent inscribed copies of his book to Trump and Clinton—speaks to the starkly different worldviews on the ballot in the 2016 presidential race. “I look at the current election campaign as a discussion on this geographical issue,” Rasmussen told me. “How can the United States make sure that the lessons learned from the Second World War can also be relevant in the 21st century?”