Roughly five minutes into his interview on Wednesday night with Fox’s Megyn Kelly, Donald Trump said something that’s crucial to understanding his political success. Kelly asked him about being a bully. Trump responded that, “I’m a counterpuncher, you understand. I’m responding. I respond by maybe, times 10. I don’t know. I respond pretty strongly. But in just about all cases I’ve been responding to what they did to me.”

It’s a claim Trump has made before. In his mind, he’s the reluctant tough guy. He minds his own business until someone else launches a dastardly attack. Then, once provoked, he shows no mercy. To many Republicans, it’s a tremendously appealing self-self-depiction. Why? Because it’s the way they depict the United States.

Walter Russell Mead begins his indispensable 1999 essay, “The Jacksonian Tradition” by describing American savagery in war. “In the last five months of World War II, American bombing raids claimed the lives of 900,000 Japanese civilians.” America killed roughly one million North Korean civilians between 1950 and 1953. “The United States dropped almost three times as much explosive tonnage in the Vietnam War as was used in the Second World War.”

Mead goes on to explain the political tradition that underlies this ferocity, which he names after President Andrew Jackson. Jacksonians, Mead argues, view America as a country that just wants to be left alone. They have little interest in the “Hamiltonian” project of prying other countries open to American commerce or the “Wilsonian” project of spreading democracy and liberty across the globe. But when attacked, especially by what they consider dishonorable foes, Jacksonians believe that “wars must be fought with all available force. The use of limited force is deeply repugnant.”

This ethic is central to the way that Americans—especially Jacksonian Americans, who dominate the Republican base—tell the story of America’s major wars. In this narrative, the United States was minding its own business until one December morning in 1941, when Japan launched a shameful sneak attack at Pearl Harbor. (Generally overlooked is the power struggle between Japan and the U.S. in East Asia. Tokyo was seeking the same kind of regional hegemony that the United States enjoyed in Latin America. The United States responded with an embargo on scrap metal and then oil).

In the Jacksonian narrative, Japan’s unprovoked attack unleashed America’s full fury. Harry Truman’s decision to use atomic weapons to force an unconditional Japanese surrender remains so publicly sacrosanct that earlier this year, when the White House announced that President Obama would visit Hiroshima, it that he would in no way apologize for America’s behavior there. Had the White House left open the possibility of American remorse, the political blowback would have been ferocious.

The standard narrative of the “war on terror” is similar: innocence followed by unprovoked attack. The United States, explained George W. Bush in his second inaugural, had been enjoying “years of relative quiet, years of repose, years of sabbatical—and then there came a day of fire.” Or as Bush declared in announcing that America was going to war in Afghanistan, “We did not ask for this mission, but we will fulfill it.”

For Jacksonians, the problem comes when America does not fulfill it. When that happens, they often blame leaders for making America’s troops fight with one hand tied their backs. On the right, this remains the dominant explanation for America’s loss in Vietnam. It also underlies the frequent Republican claim that an excessive concern for civilian casualties is preventing the Obama administration from, in Ted Cruz’s words, “carpet bomb[ing] ISIS into oblivion.”

It’s easy to see the Jacksonian ethic in Trump’s foreign policy. He’s against nation building. He couldn’t care less whether other countries are democratic. But when “animals” attack the US, he rejects virtually any moral limits on America’s response. Torture? Sure, because “You’re not going to win if we’re soft and…they have no rules.” Using nuclear weapons? Trump won’t rule it out. In a quintessentially Jacksonian moment, former Indiana basketball coach Bobby Knight praised Trump last month for being like Truman, who had “the guts to drop the bomb in 1944.”

But this alone doesn’t capture Trump’s appeal. He doesn’t just advocate Jacksonian policies. He also appears to channel the Jacksonian ethic in his personal conduct. Trump describes his political struggle in the same Hobbesian terms as he describes America’s struggle in the world. Asked by Kelly why he insults his opponents, Trump responded that, “I view myself as a person who like everyone else is fighting for survival.” He invariably describes himself as an innocent besieged by brutal, unscrupulous assailants. “I’ve been attacked pretty viciously by some of these guys,” he said last August about his GOP foes. Ted Cruz, he declared later, is a “nasty guy.” The protesters at his rallies are “bad dudes.” Fox has treated him “very unfairly.” CNN’s behavior towards him has been “very unprofessional.”

This depiction of himself as blameless, and his foes as vicious, justifies whatever Trump does in response. In the first GOP debate, Kelly quoted some of Trump’s derogatory statements about women and then asked how he’d respond when Hillary Clinton cited them in the general election. Trump described the question as a kind of violent attack: “there was blood coming out of her eyes, blood coming out of her wherever.” In his mind, this entitled him to call Kelly a “bimbo.” When Kelly asked him about that epithet on Wednesday night, he justified it as “fighting back.”

The mid-20th-century theologian Reinhold Niebuhr often argued that the greatest danger to American foreign policy was America’s presumption of innocence. If the United States recognized its sinfulness, it would accept moral limits on its power. If it didn’t, it might become like the Soviet Union, convinced that no matter how brutally it behaved, it was serving a higher good. “Pride and self-righteousness of powerful nations,” Niebuhr wrote, “are greater hazard to their success than the machinations of their foes.”

Trump is Niebuhr’s nightmare: an American leader totally devoid of moral introspection. He depicts America as preyed upon by predators and crooks, and he depicts himself the same way. Thus, whatever America does—and whatever he does—is merely self-defense. Whoever suffers is merely getting what they deserve.