Henry Kissinger often said that nuclear arms are “weapons in search of a doctrine.” After the Cold War, some strategists have tried to figure out what, exactly, these weapons could buy them beyond deterrence. The answer, as it turns out, is: nothing.Two wars taking place right now are cases in point. The ongoing American attacks on Iran and Russia’s desperate campaign of atrocities in Ukraine have produced dramatic footage of two major powers taking on middleweight military opponents, inflicting grievous damage, and yet failing to achieve their goals. Among other painful lessons, the Americans and the Russians are learning, again, that their impressive array of nuclear weapons does not offer them a victorious path out of such conflicts.Americans since the end of the Cold War haven’t bothered to think much about nuclear weapons. Last spring, the Trump administration decided to default to its 2018 Nuclear Posture Review, a report that is supposed to explain U.S. nuclear-weapons policy to Congress and the American people, rather than issue an update. But a lot has changed in almost 10 years, including the eruption of two sizable wars. Moreover, the United States is in the process of spending nearly $1 trillion on modernizing its nuclear arms without anyone spelling out what the Pentagon would do with them.The Cold War showed that strategic deterrence works to keep the peace among the nuclear-armed powers. It also showed that these arms have almost no use in regional conflicts. With two nuclear superpowers embroiled in two such wars, revisiting America’s 20th-century experiences and learning from them is crucial.The strategic nuclear standoff between the United States and the Soviet Union kept the Cold War from going hot. The Soviets and the Americans were perfectly willing to cause trouble for each other and even fight through proxies in various parts of the world, but neither side wanted events to escalate out of control and lead to complete annihilation. Even now the central mission of America’s nuclear arsenal, as the Trump administration said in 2018, is “to deter potential adversaries from nuclear attack of any scale” against the United States. Unfortunately, the Trump administration wants to leave the door open to bringing nuclear weapons into any number of scenarios. Here, the president and his team have apparently failed to learn from history.[Phillips Payson O’Brien: Putin can no longer hide his catastrophe]During the Cold War, the Americans were outnumbered by Soviet and Chinese forces. Unable to deploy forces around the globe to meet every possible instance of Communist aggression, U.S. strategists tried to figure out how nuclear weapons could be used in regional conflicts far from home. Over and over, they ran into dead ends.In Korea, the U.S. military presented both Harry Truman and Dwight Eisenhower with plans to strike targets in East Asia, including China. Both presidents backed away from the idea, not least because of the obvious escalatory dangers of triggering war with the Soviet Union. In Vietnam, Senator Barry Goldwater famously suggested using nuclear weapons to defoliate Vietnam’s jungles and expose enemy supply lines, an irresponsible idea that contributed to Goldwater’s defeat. (Johnson, whose administration was secretly considering plans to nuke China’s emerging nuclear capability in 1964, once made the dark joke to a reporter that “we can’t let Goldwater and Red China both get the bomb at the same time. Then the shit would really hit the fan.”) During the siege of Khe Sanh, the U.S. Army developed a plan, without Johnson’s knowledge, for using nuclear weapons as a last resort should American forces face being overrun. When informed of its existence, Johnson was enraged and ordered the whole business terminated.Richard Nixon, during his first year in office, asked for plans to use nuclear arms against North Korea after becoming fed up with Pyongyang’s provocations, including an April 1969 downing of a U.S. reconnaissance plane. Nixon was given various options, including precise strikes on military targets with nuclear bombs much smaller than those dropped on Japan in 1945. Once again, however, American planners could not figure out how to defang North Korea without causing ghastly destruction and risking escalation in an unstable part of the world. Nixon shelved the plan.At the end of the Cold War, the United States tried to dislodge Iraq from Kuwait, a conflict that could have entailed enemy chemical strikes on American and allied forces. American leaders never seriously contemplated the use of nuclear weapons. General George Lee Butler, the head of the U.S. Strategic Air Command at the time, later said that U.S. officials ruled out the nuclear option because their own studies had already told them that ‘‘a nuclear campaign against Iraq was militarily useless and politically preposterous.’’Today, strategists might argue that the ability to influence new types of conflicts with nuclear threats, or the actual use of nuclear weapons, is no longer limited by outdated Cold War concerns about escalation. The current undersecretary of defense for policy, Elbridge Colby, wrote in 2013 that the United States should keep the option open to respond to a major cyberattack with thermonuclear weapons. But although the Cold War is over, the problems of using nuclear weapons against non-nuclear opponents all remain.Threatening to use nuclear weapons is easy. Soviet and American leaders did it all the time during the Cold War. But figuring out where and how to use one is just as difficult today as it was 50 years ago.The difficulty of making credible nuclear threats hasn’t stopped some current leaders from trying their hand at it. When Russian President Vladimir Putin launched his war against Ukraine in the winter of 2022, he made a show of ordering his defense minister to put Russia’s strategic nuclear forces on a “special regime of combat duty.” These words had no real military meaning: No signs emerged of an elevated state of Russian nuclear readiness.Putin believed that a Russian attack against Ukraine would collapse the government in Kyiv in a matter of days, but the war quickly revealed how much the corrupt and incompetent Russian military had decayed over the past decade, and how much the Ukrainian armed forces had improved in the same period. Putin’s World War II blitz degenerated into World War I trench warfare.As the magnitude of the Russian failure became apparent inside the Kremlin, U.S. officials worried that Putin might resort to the use of battlefield nuclear weapons. Russian nuclear doctrine states that the Russian Federation would use nuclear arms only in response to “critical” threats to its sovereignty and “territorial integrity,” but Putin has been cagily flexible about what any of that really means, and he has left it to surrogates on television and in his government to make explicit threats against Ukraine and the West.[Read: Putin is slipping into delusion]Russia has no real nuclear options in the Ukrainian slog. Even Putin likely realizes that the costs would be enormous and the gains negligible. For one thing, the wind blows from Ukraine into Russia, and he would risk poisoning his own people, a problem that could lead to a revolt among terrified Russians. The United States—at least under the previous Biden administration—has warned that such an act would provoke a massive military response. And Russia friend China has warned Putin that nuclear use would be the end of any support, which would make Russia even more of a pariah state than it already is.In 2023, Russia tried playing a different game when the Kremlin confirmed that it was moving nuclear weapons into Belarus, placing them outside Russia for the first time since the end of the Cold War. Putin apparently thinks that bringing these weapons close to an active war zone might increase the sense of risk in foreign capitals. The only person whose thinking seems to have changed, however, is Alexander Lukashenko, the dictator of Belarus. Last week, he announced that Belarus would not take part in any operations against Ukraine. The warheads remain in his country, but in storage and of little use to anyone.Putin’s various nuclear manipulations have bought him nothing. The war is now in its fourth year; Russian forces, bogged down at the front, are taking immense losses, and Ukraine is striking targets deep inside Russia, including the capital itself. When Trump asked Ukrainian President Volodymyr Zelensky last week if he was willing to go to Moscow to talk with Putin, Zelensky quipped: “It’s difficult. There are a lot of Ukrainian drones there. It’s very dangerous.”A few thousand miles south of Moscow, the Iranians are inflicting a similar humiliation on the nuclear-armed Americans. Trump has issued multiple threats that could be taken to imply the use of nuclear weapons, and like Putin, he has learned that such threats generate few results but plenty of opprobrium.On April 7, Trump issued the genocidal threat that if Iran did not accede to various American demands, including opening the Strait of Hormuz, a “whole civilization will die tonight, never to be brought back again.” Only nuclear weapons can end a nation in one night, but the Iranians were unmoved; Trump’s unhinged statement instead brought global condemnation, including from Leo XIV, the first American pope. Trump reversed course within a day by claiming, baselessly, that Iran had presented “a workable basis on which to negotiate.” In May, he tried again: “If there’s no cease-fire,” he said, “you’re just going to have to look at one big glow coming out of Iran.” Again, the world reacted, but Iran did not.Trump’s threats of total destruction mean nothing, and even the enemy seems to know it. Indeed, his threats tend to come just as he’s about to capitulate, rather than escalate, so perhaps he uses them as a way of covering his retreats. Much like Putin, Trump refers to nuclear weapons but then does nothing to indicate that they are coming into play. For this, everyone should be grateful.Even if Trump were serious, however, he would face the same problem his predecessors faced in Asia and Putin faces in Ukraine: The political and economic costs of using a nuclear weapon would far outweigh any possible gains; it could generate an enormous number of casualties and bring radioactive fallout to friendly nations. American nuclear use would almost certainly rally the region—and much of the world, including NATO—against the United States.Both Iran and Ukraine are outnumbered and outgunned by every measure of military strength, and yet the U.S. and Russia are facing historic defeats. Great empires have learned over and over that conventional wars are easy to lose for many reasons, including the mismatch between the ease of inflicting damage and the difficulty of holding territory, a problem that has frustrated U.S. planners across multiple conflicts. Nuclear weapons in these regional wars have been useless. What should Americans take from these experiences?Strategic nuclear weapons will continue to be the silent guardians of a global peace among the great powers, at least until the world can think of something better. But neither the United States nor other nations need a full panoply of nuclear options for every military eventuality. The Trump administration says that the United States would consider the employment of nuclear weapons only “in extreme circumstances to defend the vital interests of the United States, its allies, and partners.”[Tom Nichols: Trump is very confused about nuclear weapons]But what is an extreme circumstance? The United States is losing a war to Iran, which might seem “extreme,” but a U.S. defeat in the Gulf does not threaten the existence of the United States. A gigantic Russian army is making war in the middle of Europe—the kind of nightmare NATO was created to forestall—but the United States is working to defeat Russia without the direct involvement of U.S. or other NATO forces. And yet, the Trump administration wants to return to Cold War thinking: It withdrew from the 1987 treaty on intermediate nuclear forces and wants to place a new, nuclear-armed cruise missile on submarines. Trump also wants his new “Trump class” battleships (assuming they ever get built) to have nuclear weapons on them, a senseless move that would return nuclear arms to America’s surface ships for the first time since the early 1990s.Nothing of consequence will be done to reform nuclear strategy while Trump is in office. But it’s not too early for the United States to look at the wars in Ukraine and Iran and draw some important conclusions.First, nuclear weapons cannot replace conventional power. China knows that the United States has nuclear weapons; what the leaders in Beijing need to see in the Pacific are ships, aircraft, personnel, and the will to defend our allies, not more nuclear warheads. The Iran war has depleted stocks of conventional U.S. attack munitions, not nuclear bombs.Second, the United States must wrench itself out of its Cold War mindset. For example, the U.S. maintains a policy of reserving the right to use nuclear weapons first, leftover from the days when NATO was sure to be overrun by Soviet tanks in Europe in the first weeks of a conflict in Europe. Today, the situation is reversed: Russia would lose a conventional war with NATO, and quickly. Nothing is gained from holding on to a strategy from a half century ago that requires the U.S., even now, to keep a stockpile of tactical nuclear weapons in Europe. (Nor should the United States deploy more nuclear weapons in the Pacific region.) At the least, a policy declaration of “no first use” would help to ground American strategy in the new realities of the 21st century.Finally, the United States needs a complete overhaul of its defense strategy. Trump has treated the entire world, including U.S. allies, as potentially hostile. His reckless and paranoid approach to security has left the United States less safe and the world less stable. The next administration will have to pick up the pieces.In the meantime, a new Congress can start examining some of the Pentagon’s requests that involve nuclear weapons—and start canceling them. One Cold War nuclear spending spree was enough.