U.S. President Donald Trump’s June 16 tweet on TruthSocial, “Everyone should immediately evacuate Tehran!” was a strategic mistake in communications and an incitement to the spread of nuclear weapons. Because it was made in conjunction with his call for the “unconditional surrender” of Iran and recent ambiguous statements by Israeli Prime Minister Benjamin Netanyahu, it gave the impression of a months-long conflict with Iran that could leave the Israelis no choice but to use nuclear weapons to end the war. The Israelis earlier called for the evacuation of the northern part of the capital, Tehran, on X (Twitter), likely with a view to reducing civilian casualties as they destroy military and nuclear infrastructure targets with bombers. Consequently, given the fear of escalation to the use of nuclear weapons, which could occur for many different reasons in this conflict, Trump’s tweet was widely misinterpreted on social media as a boastful warning about a possible nuclear attack by Israel.
There are many dangerous and unpredictable opportunities for the use of nuclear weapons in the ongoing Iranian-Israeli rivalry and periodic violent flare-ups. If Israel’s borders are ever breached by an invader, perhaps Egypt or Turkey, and it is about to collapse, it is almost certainly likely to detonate a nuclear weapon to signal that it will unleash more attacks if the invasion is not halted. Apartheid-era South Africa had built six nuclear weapons to detonate and warn the international community to stop an invasion by frontline African states, although it ultimately negotiated for peace. Israel may eventually, out of frustration, use nuclear bombs to dig out Iran’s nuclear weapons enrichment centrifuges at locations like Natanz in future raids.
Russian and Chinese warnings against attempts by the Israelis to cause regime change in Iran, perhaps replacing the Ayatollahs with Pahlevi monarchs, were implicitly about warning the U.S. not to let Israel escalate to the use of nuclear weapons. Trump’s discussion with Pakistan’s Army Chief Asim Munir on June 19 about who controls Pakistan’s 170 nuclear weapons was likely because of Washington and Tel Aviv’s nervousness about what role Pakistan would play in the conflict. Saudi Arabia likely has an arrangement to put Pakistani nuclear warheads on its DF-3 Chinese missiles deployed atal-Nabhaniyah, and it currently also has a Chinese-brokered peace deal with Iran.
There are innumerable escalation paths leading to and proceeding from a nuclear detonation. If Iran manages to assemble a primitive nuclear weapon and then it closes the Straits of Hormuz to oil tankers with mines, missiles, submarines, and patrol boats, and then the U.S. Marines conduct a landing to reopen it, and then Iran detonates a nuclear warhead on a beach to repel the Marines, Washington may be compelled to retaliate also with nuclear weapons. If either Israel, Iran, or Pakistan uses nuclear weapons against the other, the major power ally of these smaller states, Russia, China, or the U.S., may feel compelled to retaliate to show that they are committed to their allies and would not abandon them. China and Russia may back Iran to the extent of threatening Israel if Israel detonated a nuclear warhead in Iran, or Pakistan may come to back Iran while under a Chinese nuclear umbrella, as the two countries are military allies; then Israel may be compelled to attack preemptively. Israel may coordinate with nuclear weapons-armed India to conduct a conventional attack on Pakistan’s nuclear arsenal and infrastructure, which could provoke a nuclear response from Pakistan. An Indo-Pakistan nuclear war is almost certain to draw in China against India and the U.S. to retaliate on behalf of India.
If Chinese, Pakistani, or Russian aircraft or air defense missile units in Iran get entangled with Israeli or U.S. combat aircraft, then these direct encounters could escalate to attacks on the high seas and even conventional hypersonic missile attacks against mainland China or the continental United States. Missiles passing over Russia, China, or the U.S. may be misinterpreted as a small-scale nuclear attack, eliciting a prompt retaliatory response.
Leaders, including democratically elected presidents, must be careful what they say about nuclear weapons. Nuclear weapons are the most powerful weapons that have ever existed but do not automatically make a country safe. In 1969, China and the USSR fought a border war in the Far East, despite both possessing nuclear weapons. Israel was attacked in 1973 by Egypt and Syria, despite Tel Aviv possessing nuclear weapons. Argentina seized the Falkland Islands/Las Malvinas from the United Kingdom in 1982, despite the latter’s possession of nuclear weapons. There are a number of factors affecting the utility and the limits of nuclear weapons.
First, if nuclear weapons are widely perceived as immoral and repugnant, then no leader will use them. If another leader, even if they are not aggressive, knows nuclear weapons will not be used, then conventional war comes to be seen as safe because it is assumed there will be no escalation to the use of nuclear weapons. Disputes and wars will likely be more common because the costs will be seen as much lower. This effect is called the stability-instability paradox.
However, second, if leaders believe nuclear weapons can be used, then it raises the costs of war and makes it less likely that either nuclear weapons or conventional attacks will be launched. Having enough nuclear weapons to stop an opponent from attacking is called immediate deterrence. Immediate deterrence can be achieved with a small arsenal targeting the enemy’s cities and some tactical nuclear weapons for battlefield use.
Third, if leaders are afraid of an accidental nuclear launch, then they will want to minimize the number of nuclear weapons so that the probability of a mistaken attack is minimized. Also, if a leader believably promises to protect their allies, then their allies will forego building their own arsenals, reducing the total number of nuclear weapons. This will leave the nuclear weapon state with an arsenal much larger than most other states, most of whom will have no nuclear weapons, and because they are so small, they will not even consider the costs of having to build nuclear warheads to catch up with the principal nuclear weapon states. This is termed general deterrence and requires an arsenal far larger than what is required for an immediate deterrent arsenal explained above. It is also the main reason why the larger powers insist on large arsenals, not to deter an attack, but to deter attempts at building new arsenals, even among neutral countries.
When leaders are not modest about their nuclear arsenals, they make non-nuclear countries insecure and wanting to develop their own. When U.S. President Harry Truman demanded forcefully that the Soviet Union leave Iran in 1946, although he did not mention or intend a nuclear threat (as only the U.S. had atomic bombs at that time), he caused virtual panic in Moscow, which led to an unrestrained nuclear build-up. In 1971, when India was invading East Pakistan, U.S. President Richard Nixon sent the nuclear-weapons-armed aircraft carrier U.S.S. Enterprise into the Bay of Bengal to help Pakistan, unintentionally causing India to feel insecure and to detonate a nuclear device in 1974. In neither of these cases did the usually sober president intend on provocatively swaggering with nuclear weapons, but both had profound and irreversible effects on instigating nuclear proliferation.
If a U.S. president is too vocal about their reliance on the power of nuclear weapons to compel compliance, and they fail to provide assurances that nuclear weapons are instruments only of last resort, then they undermine general deterrence because smaller states are suddenly insecure and are incentivized to get their own nuclear weapons. Larger allies of the U.S., like NATO, will question the wisdom and credibility of a blustering, nuclear-armed alliance leader. A widespread proliferation of nuclear weapons to many different states makes deterrence much more difficult because of the complexity of overlapping arsenals and possible accidents. For example, if ever the U.S. launched its land-based Minuteman III ICBM missiles at China, they would have to fly over Russia’s Far East. This may be solved with a telephone call, but this solution may be far less successful with smaller states that do not possess long-range sensors or satellites.
Also, because nuclear weapons are much less expensive than large armies and navies, once they are widely deployed, they will significantly reduce the relative power of the larger nuclear-armed states. Thus, a U.S. president boasting about nuclear weapons and nuclear war, while in the short term it seems like a useful tactic of coercive diplomacy, is actually a long-term, self-defeating mistake. Trump may have convinced Russia of the riskiness of disarmament, China, Pakistan, and India of the need to accelerate the accumulation of their warhead stockpiles, Iran to finish its program covertly, and Turkey, South Korea, Brazil, Germany, Japan, and other insecure major powers to acquire their own independent arsenals.
