Units from Belarus returned home from Russia on Saturday after training on how to use the Iskander tactical missile system to launch nuclear weapons, the Belarusian defense ministry said. It made the announcement exactly four weeks after President Vladimir Putin said Russia would station tactical nuclear weapons in neighboring Belarus, sending a warning to NATO over its military support for Ukraine. In early February, Belarus said its armed forces were in autonomous control of Iskander mobile guided missile systems that Russia had already provided. But when the units were sent to Russia on April 4 for additional training, Minsk made clear their sessions would include study of "the maintenance and use of tactical nuclear warheads of the Iskander missile defense system". Those units returned to Belarus on Saturday, the defense ministry said on Telegram. Russia has not given a clear timetable for moving tactical nuclear weapons to Belarus, but Putin said the construction of storage facilities should be complete by the start of July. It will be the first deployment of part of Russia's nuclear arsenal outside its borders since the collapse of the Soviet Union in 1991.