As tensions are rising between the NATO and Russia, we hear a lot about tactical nuclear weapons lately. But people who talk about them do not appear to have a clear definition of what a tactic nuclear weapon is and they often understood it as a low yield nuclear weapon but that is not exactly so. To understand the correct meaning of a tactical nuclear weapon, I would like to point out that all nuclear weapons are categorized as strategic or non-strategic nuclear weapons. A strategic nuclear weapon is designed to be used on targets in a settled territory (a sovereign state) far away from the battle field. In general, strategic nuclear weapons have high yields which are 100 kilotons and up. 1 kiloton is approximately the energy released by the detonation of 1000 tons of TNT (equivalent to $4.184\times 10^{12}$J). Strategic nuclear weapons are delivered by intercontinental ballistic missiles (ICBM), submarine-launched ballistic missiles (SLBM), or heavy bombers. The United States is the only country that has ever used strategic nuclear weapons against a sovereign state. The United States detonated an atomic bomb called Little Boy over the Japanese city of Hiroshima on August 6th, 1945 and another atomic bomb called Fat Man over the Japanese city of Nakasaki on August 9th, 1945. The yields of Little Boy and Fat Man are, respectively, 15 kilotons and 20 kilotons. In today’s standard, they are considered low yields (for example, Russia’s non-strategic nuclear weapons have yields of 70-75 kilotons) but they were the most powerful nuclear weapons existed at that time. The two bombings resulted in the deaths of between 129,000 and 226,000 mostly civilians. All other nuclear weapons are non-strategic nuclear weapons. They are also called tactical nuclear weapons or theater nuclear weapons. As the name theater nuclear weapons suggests, they are designed for use in the battle field. Due to a possible proximity to friendly forces, they have low yields between 10 tons and 100 kilotons. According to the reference [1], non-strategic nuclear weapons have historically include bombs delivered by dual-capable aircraft (DCA) which can be used for both nuclear and conventional missions; warheads in cruise missiles delivered by non-strategic aircraft, warheads on sea-launched cruise missiles (SLCMs); warheads on ground-launched cruise missiles (GLCMs); warheads on ground-launched ballistic missiles (GLBMs) with a maximum range that does not exceed 5,500 km, including air-defense missiles (ADMs); warheads fired from cannon artillery; and anti-submarine warfare nuclear depth bombs. But the reference [1] also mentioned that today, only air-launched cruise missiles (ALCMs) and gravity bombs delivered by DCA are in the non-strategic category. I believe this statement should be understood as the case for the US non-strategic nuclear weapons. As far as I know, the lowest yield non-strategic nuclear weapon that has ever been deployed is W48. It is an AFAP (Artillery Fired Atomic Projectile) which can be fired from any standard 155mm howitzer. It had an yield of 72 tons. In the US, it was manufactured starting in 1963 and all units were retired in 1992. For the case of Russia, officially, all nuclear artillery shells have been decommissioned by the year 2000, but rumor has it that some of Soviet 152mm nuclear artillery shells like 3BV3 were not all removed in 2000 and they can be used in 152mm self-propelled howitzer 2S19 Msta-S. Also, rumor has it that Russia has been developing new 152mm nuclear artillery shells for the artillery systems on Armata platform. Even if they were all decommissioned in 2000, nuclear artillery shells are something that can be easily produced by Russia and can be immediately put to use on currently existing delivery systems. Less risking a full brown nuclear war, nuclear artillery shells can be an ideal demonstrative nuclear deterrent against the NATO in the current theater of Russian SMO (Special Military Operation) in Ukraine when the NATO crosses what Russia considers as red lines. So, I wouldn’t be surprised if Russia already has them in stock and ready for use. Thus far, non-strategic nuclear weapons have never been used.
Physics Tidbit: From the famous Einstein’s formula $E=mc^2$, we see that 1 g of mass is equivalent to $9\times 10^{13}$J of energy. Since 1 kiloton=$4.184\times 10^{12}$J, 1 g of mass is equivalent to 20.15 kilotons of energy which is about the yield of Fat Man .
References:
- Chapter 4. Nuclear Weapons, The Nuclear Matters Handbook 2020, The Office of the Deputy Assistant Secretary of Defense for Nuclear Matter
