Russia plans to hold massive war games involving 300,000 personnel next month – its biggest military manoeuvres since a Cold War drill in 1981.
Kremlin spokesman Dmitry Peskov said the drills were justified given “aggressive and unfriendly” attitudes towards his country.
Units from China and Mongolia will also take part in the exercises at military ranges in central and eastern Russia.
The manoeuvres come at a time of rising tension between Nato and Russia.
What will take place in the drills?
Defence Minister Sergei Shoigu said 36,000 tanks, armoured personnel carriers and armoured infantry vehicles would take part in Vostok-2018, from 11 to 15 September, along with more than 1,000 aircraft. “Vostok” is Russian for “east”.
All of Russia’s airborne units and two of its naval fleets will also take part in the drills across Siberia and the Russian Far East.
Mr Shoigu compared the Vostok-2018 exercises to Soviet manoeuvres in 1981, which involved a pretend attack on Nato. He said: “In some ways they will repeat aspects of Zapad-81, but in other ways the scale will be bigger.”
Mr Peskov said the involvement of Chinese units showed Russia and Beijing were co-operating in all areas.
The scale of Vostok-2018 is equivalent to the forces deployed in one of the big World War Two battles.
A smaller-scale Russia-Belarus exercise was held in western regions last year.
President Vladimir Putin has made military modernisation – including new nuclear missiles – a priority.
Russia’s armed forces are reckoned to have about one million personnel in total.
How and why will China be involved?
The Chinese defence ministry put out a fairly dry statement talking of deepening military co-operation and “enhancing both sides’ capabilities to jointly respond to various security threats”.
But it did say the exercises would “not target any third party”.
The ministry also confirmed the extent of the Chinese involvement – “3,200 troops, more than 900 pieces of military hardware as well as 30 fixed-wing aircrafts and helicopters” – and confirmed the location – the Tsugol training range in Russia’s Trans-Baikal region. Some of the forces have already arrived.
Details of the Mongolian involvement are unclear.