Smoke rises at a firing range during the Zapad-2017 war games, held by Russian and Belarussian servicemen, outside the town of Ruzhany in Belarus, September 17, 2017.

Belarussian Mi-8 helicopters fly in formation during the Zapad-2017 war games, held by Russian and Belarussian servicemen, near a firing range outside the town of Ruzhany in Belarus, September 17, 2017.

A Belarussian Mi-8 helicopter flies above a firing range during the Zapad-2017 war games, held by Russian and Belarussian servicemen, outside the town of Ruzhany in Belarus, September 17, 2017.

A Belarussian Mi-8 helicopter fires while flying above a firing range during the Zapad-2017 war games, held by Russian and Belarussian servicemen, outside the town of Ruzhany in Belarus, September 17, 2017.

Crew members operate a Belarussian Mi-8 helicopter during the Zapad-2017 war games, held by Russian and Belarussian servicemen, outside the town of Ruzhany in Belarus, September 17, 2017. REUTERS/Vasily Fedosenko

Belarussian Mi-8 helicopters fly in formation above a firing range during the Zapad-2017 war games, held by Russian and Belarussian servicemen, outside the town of Ruzhany in Belarus, September 17, 2017.

Russian President Vladimir Putin uses a pair of binoculars while watching the Zapad-2017 war games.

A parachuter descends before landing at a firing range during the Zapad-2017 war games, held by Russian and Belarussian servicemen, outside the town of Ruzhany in Belarus, September 17, 2017.

A Belarussian Mi-8 helicopter transports participants of the Zapad-2017 war games, held by Russian and Belarussian servicemen, above a firing range outside the town of Ruzhany in Belarus, September 17, 2017.