President Vladimir Putin placed the country’s strategic deterrence forces on “special” alert on Sunday, announcing the move during a meeting with Russia’s Defense Minister Sergey Shoigu and Chief of Staff Valery Gerasimov.

Russia’s deterrent forces include various strategic weapons, both nuclear and conventional, that can be used for defense and offense alike. According to Russia’s military definition, the forces are designed to “to deter aggression against Russia and its allies, as well as to defeat the aggressor, including in a war with the use of nuclear weapons.”