of impact works correctly. Range – the maximum distance from a target a weapon can be fired to successfully hit the point where it is targeted at. (When range is used without qualifiers, like maximum or minimum, it is assumed that it refers to maximum; however, many of these described weapons have minimum ranges as well, though they are not mentioned, or, in all likelihood, even known to the public.) kt/Mt – This is an approximate measure of how much energy is released by the detonation of a nuclear weapon; kt stands for kilotons TNT, Mt stands for megatons TNT. Conventional science of the period contemporary to the Manhattan project came up with these measures so as to reasonably analogize the incredible energy of a nuclear detonation in a form that would be understandable to the military, politicians, or civilians. Trinitrotoluene (TNT) was and is a high explosive with industrial and military uses, and is around 40% more powerfully explosive than an equivalent weight of gunpowder. A ton is equivalent to 1000 kg or approximately 2200 pounds. A 20 kt nuclear device, therefore, liberates as much energy as does the explosion of 20,000 tons of TNT (this is the origin of the term, for the exact definition see TNT equivalent). This is a large quantity of energy. In addition, unlike TNT, the detonation of a nuclear device also emits ionizing radiation that can harm living organisms, including humans; the prompt radiation from the blast itself and the fallout can persist for a long period of time, though within hours to weeks, the radiation from a single nuclear detonation will drop enough to permit humans to remain at the site of the blast indefinitely without incurring acute fatal exposure to radiation. Likely first strike weapons systems Because of the low accuracy (large circular error probable) of early generation intercontinental ballistic missiles (and especially submarine-launched ballistic missiles), counterforce strikes were initially only possible against very large, undefended targets like bomber airfields and naval bases. Later generation missiles with much improved accuracy made counterforce attacks against the opponent's hardened military facilities (like missile silos and command and control centers) possible. This is due to the inverse-square law, which predicts that the amount of energy dispersed from a single point release of energy (such as a thermonuclear blast) dissipates by the inverse of the square of distance from the single point of release. The