On Monday, the NATO military alliance will hold a training exercise, known as Steadfast Noon, in which US B-52 bombers and F-16 fighters will simulate dropping atomic bombs over Europe amid a deepening nuclear standoff with Russia.

The training exercise comes just ten days after US President Joe Biden warned of a nuclear “apocalypse,” saying the risk of nuclear war is the greatest since the Cuban Missile Crisis of 1962.

“This is the exercise that practices NATO’s nuclear strike mission with dual-capable aircraft and the B61 tactical nuclear bombs the US deploys in Europe,” wrote Hans Kristensen of the Federation of American Scientists.

The aircraft will rehearse dropping B61 “tactical” thermonuclear bombs, each of which is up to 20 times more powerful than the weapon that destroyed Hiroshima in World War II, killing as many as 126,000 civilians.

While nuclear training exercises are usually presented as routine, nonthreatening, and not targeting any specific country, this year NATO Secretary-General Jens Stoltenberg made clear that the exercise is intended as a threat to Russia.