Vladimir Putin has watched Russia's biggest military manoeuvres since Soviet times, involving 160,000 troops and about 5,000 tanks across Siberia and the far eastern region in a massive show of the nation's resurgent military might.
Dozens of Russia's Pacific Fleet ships and 130 combat aircraft also took part in the drills, which will continue through the week. The Russian president watched some of the drills on Sakhalin Island in the Pacific, where thousands of troops were ferried and airlifted from the mainland.
Deputy defence minister Anatoly Antonov assured foreign military attaches that the exercise was part of regular combat training and was not directed against any particular nation, though some analysts believe the show of force was aimed at China and Japan.
Mr Antonov said Moscow warned its neighbours about the exercise before it started, and provided particularly detailed information to China in line with an agreement that envisages a mutual exchange of data about military activities along the 2,700-mile border.
The two Cold War-era rivals have forged what they described as a "strategic partnership" after the 1991 Soviet collapse, developing close political, economic and military ties in a shared aspiration to counter US power around the world.
Russia has supplied sophisticated weapons to China, and the neighbours have conducted joint military drills, most recently a naval exercise in the Sea of Japan earlier this month.
Despite close economic ties and military co-operation, many in Russia feel increasingly uneasy about the growing might of its giant eastern neighbour.
Some fear that Russia's continuing population decline and a relative weakness of its conventional forces compared with the Chinese People's Liberation Army could one day tempt China to grab some territory.
The manoeuvres are part of recent efforts to boost the military's mobility and combat readiness after years of post-Soviet decline, but they have far exceeded previous drills in numbers and territorial scope.
As part of the war games held across several time zones, some army units deployed to areas thousands of miles away from their bases.