Russia launched its largest nuclear exercises in years on Tuesday, mobilizing nearly 65,000 troops, over 200 missile launchers, 140 aircraft, 73 surface vessels and 13 submarines, including eight strategic nuclear submarines, in a three-day drill that runs through Thursday.

The Russian Defense Ministry announced the maneuvers without prior public notice on May 19, framing them as a rehearsal for “the preparation and use of nuclear forces in the event of a threat of aggression.” The exercises involve the Strategic Missile Forces, the Northern and Pacific Fleets, Long-Range Aviation Command, and units from the Leningrad and Central Military Districts, according to the ministry statement. Live launches of ballistic and cruise missiles at ranges inside Russia are planned as part of the drills.

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