President Vladimir Putin has been watching Russian military manoeuvres in the Black Sea region just hours after he ordered the snap exercise.
Officials in Moscow said the surprise move was to keep personnel on their toes and to test the capabilities of their hardware.
It also sends a powerful military message to Russia’s neighbours and the west.
The Black Sea coast includes Georgia, Ukraine, Turkey, Bulgaria and Romania.
A military spokesman said 36 warships would take part along with an unspecified number of aircraft but he did not say how long the wargames would last.
Russia’s Black Sea fleet is based in the former Soviet port Sevastopol, a vital stepping off point for a war against Georgia in 2008. These exercises are in neighbouring Krasnodar.
It is perhaps no coincidence that the Americans are also in the region, training with Georgian troops on an operation that became an annual event after that conflict.
Around 350 US Marines have been helping troops prepare for deployment to Afghanistan where Georgia has had a contingent since 2004.
It underlines Georgia’s desire for closer ties with NATO.