In 1944, Leslie Groves, the US army general who managed the Manhattan Project, asked its chief scientist, J. Robert Oppenheimer, just how powerful their new bomb might be. Would it be 10 times as powerful as the largest bomb of the time, the RAF’s Tallboy “earthquake bomb”? Or 50 times, or even 100 times? Oppenheimer replied that he could not be sure — at the time, there were even fears that the explosive chain reaction might never stop — but he expected a bomb much more powerful than 100 Tallboys. Groves immediately replied that such a powerful weapon would not be of much use to anyone, because the “politicians” would never dare to use it.
In the short run, Groves was wrong, while Oppenheimer’s guess was correct. The Hiroshima uranium bomb was in fact more powerful than 1,000 Tallboys, with the Nagasaki plutonium bomb exceeding even that. But only five years later, Groves’s prediction came to pass. First the United States, and then the Soviet Union, and then each successive nuclear power came to the realisation that their nuclear weapons were too powerful to be used in combat. This has remained true in the decades since — all the way up to the invasion of Ukraine. For, despite Putin’s atomic sabre-rattling, he too is subject to the logic of Groves’s prediction. Decades after his conversation with Oppenheimer, a brief historical summary of nuclear war has much to teach us about the situation in Ukraine — and how victory might only be attainable there through much more conventional means.
The first test of the nuclear age came with the Korean War. In December 1950, hundreds of thousands of Chinese soldiers crossed the River Yalu to support their North Korean allies against the US. With America in immediate danger of losing tens of thousands of men, General Douglas MacArthur decided that he had to use nuclear weapons to stop the Chinese. By far the most respected US military leader of the time — he had led American forces in the Pacific from humiliating defeat to total victory, and then acted as Japan’s de facto Emperor in reforming the country — MacArthur expected Truman to assent to his superior military judgment. Instead, the answer was a flat no. MacArthur insisted, and he was dismissed.
Truman recognised that the nature of warfare had fundamentally changed since Hiroshima and Nagasaki. When he authorised those strikes, neither he nor anyone else knew that the explosions would also cause radiation fallout, which would sicken and even kill thousands of people miles from the site of the detonation. Moreover, in 1945, Truman was facing the prospect of losing many more American troops in the conquest of Japan than in the entirety of the Second World War up to that point. The Japanese really did fight to the last man, and still had 2 million troops to expend. Truman would have been thrown out of the White House if he had allowed the deaths of hundreds of thousands of Americans by refusing to use the bomb.
But five years later, the situation was very different. Facing catastrophe in Korea, Truman had the alternative of evacuating US troops to Japan if all else failed — and therefore never even considered using atomic weapons. Under the next president, his fission bombs evolved into thermonuclear fusion bombs at least 100,000 times more powerful than Tallboy. But that only made Truman’s “No” of 1950 even more definitive. Nuclear abstinence became the only possible choice for Americans and Russians alike, as the Cuban Missile Crisis precariously but definitively showed.
However, it would take much longer for this logic to develop into a definitive doctrine. Following the establishment of Nato 75 years ago today, and especially in the Sixties and Seventies, exhaustive efforts were made to extract some additional advantage from nuclear weapons and somehow gain the upper hand for the new Western alliance. So-called “tactical” nuclear weapons were made not more, but much less powerful, supposedly to enable their use on the battlefield. Their advocates claimed that they could provide firepower very cheaply, with small nuclear warheads replicating the effect of hundreds of howitzers. Both the US and Soviet armed forces duly acquired thousands of nuclear weapons: not only “small” bombs for fighter-bombers, but also bombardment rockets (some small enough to be carried in a jeep), anti-aircraft missiles, torpedoes, and even portable demolition charges.
But this illusion could not be sustained. Military planners came to understand that if US commanders tried to defend Nato territory by attacking invading Soviet forces with small “tactical” nuclear weapons, the Russians would use their own arsenal to destroy the defending Western forces. The same would apply for any attempt to replace conventional military force with nuclear weaponry. And so it was understood that, while nuclear weapons are a useful deterrent, they can only be used to strike back against a prior nuclear attack — and never to achieve any kind of victory. Thus in the Seventies, when the United States and the Soviet Union were engaged in the elaborate and highly publicised “Strategic Arms Limitation” negotiations, officials on both sides quickly agreed to quietly stop developing, manufacturing and fielding new “tactical” nuclear weapons, before equally quietly disassembling tens of thousands of these weapons.
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