A tactical nuclear weapon (or TNW) refers to a nuclear weapon which is designed to be used on a battlefield in military situations. This is as opposed to strategic nuclear weapons which are designed to threaten large populations, damage the enemy's ability to wage war, or for general deterrence. Tactical nuclear weapons are generally considered part of a strategy of limited, rather than total, nuclear war.
Tactical weapons include not only gravity bombs and short-range Army missiles, but also artillery shells, land mines, depth charges, and torpedoes for anti-submarine warfare, with nuclear warheads. Also in this category were the former nuclear-warheaded surface-to-air missiles (SAMs), ground-based or shipborne, and air-to-air missiles.
Small, two-man portable, or truck-portable, tactical weapons (sometimes misleadingly referred to as suitcase nukes), such as the Special Atomic Demolition Munition, have been developed, although the difficulty of combining sufficient yield with portability could limit their military utility. In wartime, such explosives could be used for demolishing "choke-points" to enemy offensives, such as at tunnels, narrow mountain passes, and long viaducts.
Other new tactical weapons undergoing research include earth penetrating weapons which are designed to target enemy-held caves or deep-underground bunkers.
The yield of tactical nuclear weapons is generally lower than that of strategic nuclear weapons, but they are still very powerful, and some variable-yield warheads serve in both roles. Modern tactical nuclear warheads have yields up to the tens of kilotons, or potentially hundreds, several times that of the weapons used in the atomic bombings of Hiroshima and Nagasaki.
Some tactical nuclear weapons have specific features meant to enhance their battlefield characteristics, such as variable yield which allow their explosive power to be varied over a wide range for different situations, or enhanced radiation weapons (the so-called "neutron bombs") which are meant to maximize ionizing radiation exposure while minimizing blast effects.
The development of tactical weapons has often been criticized along a number of grounds. Many have argued that the promise of being able to wage a "limited" nuclear war with tactical weapons is dangerously misleading, and that any confrontation between nuclear powers could lead to escalation and eventually the use of strategic weapons. Additionally, the small size of many tactical weapons make them potential targets for theft and nuclear terrorism, especially during times of political instability (such as the case of Russia immediately after the dissolution of the Soviet Union). Tactical nuclear weapons have in the past made up a large part of the nuclear arsenals of the United States, the Soviet Union, the United Kingdom, and France, and they were a major part in the peak stockpile levels in the 1960s. For example, the British Army of the Rhine in Germany formerly was nuclear-armed, but not anymore.
Conversely, some theorists argued during the Cold War that without tactical nuclear weapons, the United States and the United Kingdom would not have had a credible threat against the large armies of the Soviet Union, since it was unlikely that they would want to be the first to use strategic nuclear weapons in warfare. Because many felt that the use of any nuclear weapons against the Soviet Union would have triggered an exchange of strategic missile launches, though, the practical distinctions between tactical and strategic weapons might not have existed, in a way.