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 exercise, which began 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 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.

Konstantin Sivkov, a retired officer of the Russian military’s General Staff, told the daily Nezavisimaya Gazeta that the Sakhalin part of the maneuvers was intended to simulate a response to a hypothetical attack by Japanese and U.S. forces.

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 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 with the Chinese People’s Liberation Army could one day tempt China to grab some territory.

Alexander Khramchikhin, an independent Moscow-based military analyst, said that the massive exercise held in the areas along the border with China was clearly aimed at Beijing.

“It’s quite obvious that the land part of the exercise is directed at China, while the sea and island part of it is aimed at Japan,” he said.

Khramchikhin, who recently posted an article painting a grim picture of Russia being quickly routed in a surprise Chinese attack, said that the war games were intended to discourage China from harboring expansionist plots.

“China may now think that Russia has finally become more aware of what could happen,” he said, describing the exercise as a sobering signal.

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. Paratroopers were flown across Russia in long-range transport planes, and some units were ferried to Sakhalin under escort of navy ships and fighter jets.

A decade of post-Soviet economic meltdown has badly crippled Russia’s military capability, grounding jets and leaving navy ships rusting in harbors for lack of funds to conduct training. Massive corruption and vicious bullying of young conscripts by older soldiers have eroded morale and encouraged widespread draft-dodging.