Nuclear Powers, Conventional Wars: The Dangerous Erosion of Deterrence - Carter Malkasian and Zachary Constantino Foreign Affairs

 Nuclear Powers, Conventional Wars: The Dangerous Erosion of Deterrence

Carter Malkasian and Zachary Constantino

Foreign Affairs, July 17, 2025

CARTER MALKASIAN is Associate Professor of Strategy and Policy at the National War College. He is the author of The Korean War: 1950-53. The views expressed here are his own.

ZACHARY CONSTANTINO is a South Asia analyst and has served as a Senior Adviser in the U.S. Departments of Defense and State.

 

The past two months have witnessed a remarkable spike in warfare involving nuclear powers. From May 7 to May 10, India and Pakistan exchanged artillery fire, bombs, cruise missiles, and drones in their most intense round of combat since 1999. Then, on June 1, Ukraine executed a sophisticated covert operation, deploying drones positioned deep within enemy territory to attack bombers that Russia might depend on if it were ever to launch a nuclear strike—an unprecedented direct assault on a country’s means of nuclear deterrence. And on June 13, 200 Israeli aircraft carried out a surprise attack on Iranian nuclear facilities and strategic targets. Iran retaliated by sending hundreds of ballistic missiles and drones toward Haifa, Tel Aviv, and military installations in the heart of Israel. Although only a few dozen breached Israeli and U.S. air defenses, Iran’s response amounted to the largest military attack ever launched on the homeland of a nuclear power.

These clashes are the latest examples of an overall rise in conflicts that carry risks of nuclear escalation. First, nonnuclear powers are attacking nuclear powers in unprecedented and aggressive ways. Even more concerning, nuclear powers are directly trading blows. These trends raise concerns that the eight-decade moratorium on large-scale war between nuclear powers has ended. Although it is too early to tell whether another great-power war is on the horizon, the dangers of nuclear escalation are unmistakable. Clashes involving nuclear powers now echo the Cold War’s most dangerous moments. A realistic possibility is that today’s clashes become a new normal, with an elevated risk of events spinning out of control.

The failure of nuclear weapons to deter Iran from launching missiles at Israel—or Ukraine from conducting operations inside Russia—suggests that even if Iran obtained a nuclear weapon, it might not protect the country from further attacks. It also calls into question the ability of the United States to rely on its nuclear arsenal to prevent attacks from nuclear adversaries such as China, North Korea, or Russia.

This new normal requires politicians, generals, spy chiefs, and diplomats to adopt new strategies to de-escalate conflicts before they become crises. Military and civilian leaders alike need to redouble efforts to improve communication and confidence-building measures, such as notifying adversaries of military activities and hosting regular official dialogues. The United States and its allies should also retain a range of military capabilities that can counter enemy aggression without having to escalate. Leaders should conduct more of their “kinetic” actions—such as special operations raids or drone strikes in enemy territory—behind the scenes, where more off-ramps exist to manage tensions than in the public eye. These recalibrations will help offset the growing danger of a potential nuclear catastrophe.

THE END OF AN ERA

For eight decades, there has been no major war between nuclear powers. Nuclear powers have on occasion attacked nonnuclear ones, such as when the United States invaded Iraq in 2003 or China went into Vietnam in 1979. Nonnuclear powers have even attacked the military forces of nuclear states, but these challenges have taken place on battlegrounds far from home. In 1950, North Korea assaulted U.S. Army regiments in South Korea, and in 1983, Argentina attacked British forces in the Falklands. Yet the Americans, the British, the Chinese, the French, and the Soviets generally avoided direct combat with one another, even over peripheral interests.

Consequently, many analysts, scholars, and presidents concluded that both nuclear and conventional war between nuclear powers was highly unlikely. In 1958, U.S. President Dwight Eisenhower told his cabinet that “a nice, sweet, World War II type of war” seemed “very unrealistic.” As the political scientist Robert Jervis wrote in his 1984 book, The Illogic of American Nuclear Strategy: “Because nuclear war cannot be easily controlled or compartmentalized, the fear of nuclear war does deter the other side from much more than nuclear attack. Irrational as it may be, the chance of devastation has made our world unusually safe.” This dominant line of scholarly thinking, of course, has not stopped militaries from planning for a major war. One of the great ironies of the past 80 years is that nuclear powers have expended huge sums preparing for conventional wars that their nuclear arsenals had supposedly ruled out.

Nuclear weapons, however, have never completely deterred war between nuclear powers. The political scientist Robert Powell’s game theory model of conventional war and nuclear escalation, for example, has shown that the possibility of conventional war between nuclear powers depends on the level of risk and the balance of resolve. Indeed, nuclear powers engaged in periodic fighting during the Cold War.

The most intense combat between the Soviet Union and the United States occurred in the skies over China and North Korea during the Korean War. The Soviet Union lost 355 aircraft and 120 pilots, although it never officially acknowledged any involvement in the war. Other clashes between nuclear powers were tense but did not escalate into major conflicts. During the Cuban missile crisis, Soviet air defense units attacked U.S. aircraft and shot down a U-2 spy plane. Even riskier, a U.S. destroyer dropped depth charges on a nuclear-armed Soviet submarine. During the Vietnam War, Chinese antiaircraft gunners routinely shot at American planes over North Vietnam, and Chinese aircraft engaged U.S. jets that crossed into Chinese airspace. In total, American bombs killed or wounded roughly 5,000 Chinese troops. During the so-called War of Attrition that Israel and Arab states fought from 1967 and 1970, and again during the Yom Kippur War in 1973, Soviet surface-to-air missiles around the Suez Canal intercepted Israeli aircraft, Israeli and Soviet fighters tangled in dogfights, and Soviet special forces conducted raids in the Sinai. Border skirmishes between China and the Soviet Union in the 1969 Sino-Soviet conflict resulted in hundreds of casualties.

India and Pakistan have continued to clash frequently along their disputed border, even after both countries developed nuclear weapons. The largest incident of ground combat between nuclear powers occurred in 1999 in the mountainous Kargil section of Kashmir. Pakistan dispatched around 4,500 soldiers posing as local rebels to seize the high ground, which Indian personnel had vacated for the winter to avoid the extreme weather conditions. The ensuing battle involved artillery shells, infantry battles, and airstrikes. The two countries suffered over 3,000 casualties before Washington’s intervention and Indian resolve forced Pakistan to back down.

NUCLEAR NONDETERRENCE

Events during the past ten years have increased the risks of direct conflict between major nuclear powers. Russia and the United States fought on opposite sides of the Syrian civil war after Russia first intervened in October 2015. The two powers battled each other in February 2018, when Russian paramilitary troops and Syrian tanks attacked U.S. special operations forces and marines. Between 200 and 300 Russians and Syrians were killed in the largest ground engagement to date between Americans and another nuclear power.

The war in Ukraine has further revealed the limits of nuclear deterrence. A Russian aircraft downed a U.S. surveillance drone over the Black Sea in March 2023, and U.S.-provided missiles and intelligence have enabled Ukrainian battlefield strikes against Russian forces. Ukraine has repeatedly hit Moscow and petroleum storage facilities in Russia. When a Ukrainian drone struck a Russian radar installation linked to Moscow’s early warning system for incoming nuclear missiles in 2024, some analysts feared Russia would interpret the attack as a proxy action by the United States to degrade Moscow’s strategic deterrents. And on June 1, a Ukrainian drone operation damaged or destroyed as many as 30 bombers and airborne command-and-control aircraft deep within Russian territory, including planes that can carry cruise missiles. Even after Moscow lowered the threshold in its official doctrine regulating the use of nuclear arms—and despite Russian President Vladimir Putin’s saber rattling—Russian nuclear weapons have not stopped Ukraine from targeting the home territory of a nuclear power or attacking its early warning systems or strategic bombers.

Nuclear weapons have never completely deterred war between nuclear powers.

Israel’s nuclear weapons have failed to stop escalating warfare in the Middle East. In the two years before the war between Iran and Israel flared up again in June, Hezbollah (Iran’s Lebanon-based ally) and Iranian-backed Houthi rebels in Yemen sent drones and rockets into Israel in response to the war in Gaza. In April and October 2024, Iran and Hezbollah fired hundreds of missiles into central Israel. After Israel’s surprise attack against Iran in June killed leading military officials and scientists and damaged or destroyed nuclear facilities, military headquarters, and ballistic missile launchers, Iran targeted Tel Aviv and other areas in Israel with drones and ballistic missiles. The clash escalated as Israel bombed Iranian oil and gas infrastructure; Iran, in turn, launched hundreds more ballistic missiles at Israeli cities that resulted in at least 400 civilian casualties. Even if Iran pulled its punches because it feared nuclear escalation, its volleys into Israel marked the first time that cities of a nuclear power had been struck so heavily. Israeli threats to seek regime change in Tehran and direct U.S. strikes on Iranian nuclear sites demonstrated that further escalation was possible. Only after the U.S. intervened militarily and did not respond to Iran’s telegraphed strike on the U.S. base in Qatar did Iran back down and agree to a cease-fire.

The dangers of escalating violence between India and Pakistan are also growing. Regular skirmishes between India and Pakistan flared up in 2019 when India bombed a suspected militant compound inside northwest Pakistan in response to a terrorist suicide attack in Indian-administered Kashmir. This May, India launched airstrikes in Pakistan’s largest province in retaliation for another terrorist attack in Kashmir. Tit-for-tat strikes followed, including an Indian salvo on Pakistan’s Nur Khan Air Base only a few miles from one of Pakistan’s high-level command-and-control nodes. The four-day clash represented a new level of escalation: both sides attacked multiple locations within the homeland of the other for the first time since the India-Pakistan war of 1971, which took place before either country had a nuclear arsenal. In the initial wave of Indian strikes, Delhi employed cruise missiles, glide bombs, artillery, and drone-delivered munitions to strike militant infrastructure, including near major cities in Pakistan’s Punjab Province. India proved able to penetrate Pakistan’s air defense system, but Pakistan reportedly took down multiple Indian aircraft.

LOWERING THE TEMPERATURE

So far, conflicts between nuclear powers have been limited to skirmishes, low-level ground combat, air-to-air engagements, and airstrikes or missile exchanges—a far cry from the major wars of the twentieth century. But the increasing frequency of conflicts over the past ten years creates more chances for nuclear powers to find themselves ensnared in a larger war. Each time an attack strikes Israeli, Pakistani, or Russian territory, the potential for escalation jumps. Nuclear powers may feel that they have to send louder, more violent signals to be heard above the din of innumerable smaller clashes.

Policymakers need to recognize the high risk of escalation in a world of frequent conflicts involving nuclear powers. Even if neither party to a conflict wants war, each may find it difficult to avoid escalation, especially in a fast-moving crisis. Nationalistic domestic media environments, the greater use of autonomous aircraft, and the intermingling of nuclear and conventional infrastructure in many countries have further compounded the risk. And any conflict involving nuclear powers carries the inherent possibility of nuclear war.

To reduce the potential for rapid escalation, leaders should improve crisis communication, especially between India and Pakistan and China and the United States. Governments can build better guardrails by notifying their adversaries of military activities, promoting regular dialogue among officials, and improving their understanding of opponents’ redlines. For example, Gulf states have facilitated backchannel discussions between India and Pakistan that can buffer against the next crisis. These conversations are not intended to generate breakthroughs, but they can lower tensions and explore potential shared solutions to avoiding crises free of domestic political pressures.

The United States and its allies will also need to retain a set of military capabilities—including drones, special operations forces, missile defenses, and long-range strike systems—to respond to conventional action without resorting to higher levels of force. A robust menu of military options to retaliate against attacks allows the United States and its allies to fight at a level in which the risk of escalation is relatively manageable.

Finally, leaders should consider operating more covertly. The political scientists Austin Carson and Keren Yarhi-Milo have argued that backchannel signals sent through covert actions or quiet diplomacy can avoid public pressure that impedes concessions when actions are out in the open. The Cold War habit of keeping clashes quiet and not publicizing military actions may be worth reinstituting.

The end of the recent war between Iran and Israel highlights the importance of strategic de-escalation. The U.S. decision to forgo further retaliation and insist on a cease-fire after Iran’s perfunctory strike on the American base in Qatar prevented greater escalation. Diplomacy between the parties through both direct and indirect channels facilitated the cease-fire agreement. And Israel’s air defense systems and targeted strikes on Iran’s missile command-and-control network likely also narrowed Iran’s options for retaliation even before U.S. bombs damaged Iran’s underground nuclear sites.

In a world of weaker nuclear deterrence, governments must take deliberate steps to de-escalate tensions. Otherwise, each new border clash or drone strike could spark a disaster. The fact that the conflicts of the past two months did not spiral into protracted, large-scale wars is no guarantee that the next outbreak of violence will end similarly.