Since former US Secretary of State Henry Kissinger died on November 29, 2023 there has been much commentary on his legacies, whether praiseworthy (e.g. rapprochement with China) or questionable (e.g. interventions in Cambodia and Chile). But, surprisingly, there has been little or no reflection on Kissinger's contribution to the theory of nuclear war, though that contribution today seems embedded in established policy.
In 1975, while a professor of government at Harvard, Kissinger wrote Nuclear Weapons and Foreign Policy, published by the Council on Foreign Relations. President Richard Nixon admired the book, with its call for nuclear war with rules, and brought Kissinger into his inner circle, launching his career in government.
Kissinger's book starts like an argument against use of nuclear weapons, detailing the horrors that a nuclear war would inflict on people subject to one, but soon the focus transitions to a discussion of two types of nuclear weapon: "strategic" and "tactical." The terms denote how many "kilotons" are contained in each type (one kiloton equals the explosive power of 1,000 tons of TNT). Strategic nukes, designed to engage in hypothetical global conflicts, deliver from 100 kilotons to one megaton (one million tons of TNT force). The less powerful tactical nukes, designed for confined engagements, deliver from 10 to 100 kilotons.
Kissinger saw little practical use for the giant strategic nukes developed by the U.S. and Russia after World War II (the newest from the U.S., the Sentinel ICBM, delivers 300 kilotons). Instead he advocated for international agreements between potential nuclear adversaries on "limited" nuclear war, with pre-established objectives in designated areas, using only tactical nukes. This would, theoretically, keep the conflict from wiping out the whole world, merely wiping out parts of it.
Kissinger dryly explained, "The aim would be the attainment of certain conditions which are fully understood by the opponent." For instance the objective might be limited to destruction of a fleet of warships or a column of tanks, and the response might be limited to targeting a command center or a grouping of troops, with the objectives of each side understood by the other in advance.
We may have the unfolding of this idea in Russian President Vladimir Putin's announcement on June 16, 2023 that he is deploying tactical nuclear weapons in Belarus near the Ukrainian border. Putin has warned that the weapons could be used in Ukraine. If that happens, it will likely elicit a tactical nuclear response from the US and the other NATO nuclear powers, France and the UK.
Kissinger may have died on the eve of the realization of his nuclear war concept.
"Realpolitik," said to be Kissinger's philosophy of governance, is defined by Mirriam-Webster as an approach "in which diplomatic or political policies are based primarily on considerations of given circumstances and factors, rather than strictly followed ideological, moral, or ethical premises." It's fair, then, to ask what the practical, real world outcome would be from a nuclear war that follows Kissinger's parameters.
This question is remarkably easy to answer; one need only consider that the bombs dropped on Hiroshima and Nagasaki in World War II were, by Kissinger's definitions, tactical. The Hiroshima bomb was 16 kilotons, and the Nagasaki bomb was 25. The range of today's tactical nuclear weapons- as noted, 10 to 100 kilotons- thus delivers up to three times the force used on Japan. It's a stretch anyway to conceive of the World War II bombs as tactical, in the sense of contained. In Hiroshima, from a civilian population of 250,000 it was estimated that 45,000 died on the day of the blast, and a further 19,000 died from radioactive contamination during the subsequent four months. In Nagasaki, out of a population of 174,000, on the first day 22,000 died and another 17,000 within four months.