Russia’s Defense Ministry said Monday that the military would hold drills involving tactical nuclear weapons — the first time such an exercise has been publicly announced by Moscow.

A look at tactical nuclear weapons and the part they play in the Kremlin’s political messaging.

WHAT ARE TACTICAL NUCLEAR WEAPONS?

Unlike nuclear-tipped intercontinental ballistic missiles that can destroy entire cities, tactical nuclear weapons for use against troops on the battlefield are less powerful and can have a yield as small as about 1 kiloton. The U.S. bomb dropped on Hiroshima during World War II was 15 kilotons.

Such battlefield nuclear weapons — aerial bombs, warheads for short-range missiles or artillery munitions — can be very compact. Their small size allows them to be discreetly carried on a truck or plane.

Unlike strategic weapons, which have been subject to arms control agreements between Moscow and Washington, tactical weapons never have been limited by any such pacts, and Russia hasn’t released their numbers or any other specifics related to them.