Su-34 fighter jets fly during the Center-2019 military exercises in Orenburg region, Russia, on Sept. 20, 2019. Tsentr-2019 (Center-2019) military exercises involving eight countries began on Monday in Russia, Kazakhstan and Tajikistan, the Russian Defense Ministry said in a statement on Tuesday. (Photos: Xinhua)

Explosions on the battlefield are seen during the Center-2019 military exercises in Orenburg region, Russia, on Sept. 20, 2019. A total of 128,000 troops, more than 20,000 units of weapons and military hardware, about 600 aircraft and up to 15 ships and support vessels are scheduled to take part in the drills on several training grounds in the three countries and the Caspian Sea.

A helicopter Mi-8 goes to a position during the Center-2019 military exercises in Orenburg region, Russia, on Sept. 20, 2019.

A Russian multiple rocket launcher TOS-1A launches a rocket during the Center-2019 military exercises in Orenburg region, Russia, on Sept. 20, 2019.

A helicopter Mi-28 shoots a target during the Center-2019 military exercises in Orenburg region, Russia, on Sept. 20, 2019.

Soldiers descend from a Mi-8 during the Center-2019 military exercises in Orenburg region, Russia, on Sept. 20, 2019.