Russia's biggest military exercise since the Cold War, involving about 300,000 service personnel, is getting under way in eastern Siberia.
China is sending 3,200 troops to take part in "Vostok-2018", with many Chinese armoured vehicles and aircraft. Mongolia is also sending some units.
The last Russian exercise of similar scale was in 1981, during the Cold War. But Vostok-2018 involves more troops.
It comes at a time of heightened Nato-Russia tensions.
Relations between Russia and the North Atlantic Treaty Organisation (Nato) - a 29-member defence alliance dominated by the US - have worsened since Russia annexed Crimea from Ukraine in 2014.
What is Nato?
Kremlin spokesman Dmitry Peskov said the drills were justified given "aggressive and unfriendly" attitudes towards Russia.
What will happen in the drills?
The Russian defence ministry says 36,000 tanks, armoured personnel carriers and armoured infantry vehicles will take part in Vostok-2018, from 11 to 17 September, along with more than 1,000 aircraft. Vostok is Russian for east.
The exercise will be spread across five army training grounds, four airbases and areas in the Sea of Japan, Bering Straits and Sea of Okhotsk. Up to 80 naval vessels will take part, from two Russian fleets.
The drills will not be near the disputed Kuril islands north of Japan, Russia says.
The ministry's TV channel Zvezda says three brigades of Russian paratroops will play a key role, during drills at the Tsugol military range, near Russia's borders with China and Mongolia. by https://www.bbc.com/news/world-europe-45470460