President Vladimir Putin on Tuesday watched Russia's biggest military maneuvers 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 began on Friday and continue through this week. Putin watched some of the drills on Sakhalin Island in the Pacific, where thousands of troops were ferried and airlifted from the mainland.
Russia's Deputy Defense Minister Anatoly Antonov assured foreign military attaches on Monday that the exercise was part of regular combat training and wasn't directed against any particular nation, though some analysts believe the show of force was aimed at China and Japan.
Antonov said that Russia had warned its neighbors 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 4,300-kilometer (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 U.S. power around the world.
Russia has supplied sophisticated weapons to China, and the neighbors have conducted joint military drills, most recently a naval exercise in the Sea of Japan earlier this month.
But despite close economic ties and military cooperation, many in Russia have felt increasingly uneasy about the growing might of its giant eastern neighbor.
Some fear that Russia's continuing population decline and a relative weakness of its conventional forces compared to the Chinese People's Liberation Army could one day tempt China to grab some territory.
Russia and China had territorial disputes for centuries. Relations between Communist China and the Soviet Union ruptured in the 1960s, and the two giants fought a brief border conflict in 1969.
Moscow and Beijing signed a new border treaty in 2004, which saw Russia yielding control over several islands in the Amur River. Some in Russia's sparsely populated far east feared that the concessions could tease China's appetite.
Alexander Khramchikhin, an independent Moscow-based military analyst, said that the massive exercise held in the areas along the border with China was aimed at Beijing.
The maneuvers 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 both numbers and territorial scope.
As part of the war games held across several time zones, some army units deployed to areas thousands of kilometers away from their bases.