By Nick Childs
BBC World Affairs correspondent
The exercises bring together two former ideological enemies
The Russian and Chinese armed forces have begun their first joint military exercises.
Marines will storm beaches and paratroopers will descend in a mock invasion of an imaginary country.
The eight-day operation got underway with consultations between military delegations from the two countries in Vladivostok, in Russia's far east.
Analysts say China and Russia are signalling they are prepared to counter US dominance in international affairs.
The Russian and Chinese military exercises starting this week are clearly a significant step for both countries.
Even in purely military terms, they appear ambitious.
They also add some substance to the political rhetoric that is now emerging from these two formerly uneasy and even hostile neighbours of a new strategic partnership.
And they underscore a common view of the desirability of a multipolar world in which there is some counterweight to US power.
Still, officially, the scenario for these exercises - aid to an imaginary state suffering political violence - is not aimed against any specific country.
China's military has been modernising rapidly. And, while the Washington regularly sounds alarm bells about China's growing military strength and says it will be keeping an eye on events, it also insists it is not particularly worried.
The Taiwanese, too, will be watching these exercises closely, although they are being held at some distance from Taiwan itself, and there is no appetite in Russia to be sucked into the island's argument with China.
There are specific practical benefits for both participants in these manoeuvres.
For the Russians, they are a showcase for possible further arms sales to Beijing.
For the Chinese, they're a chance to participate in the kind of complicated operations that are an increasing priority for them.
But there are clear limits to all of this.
These manoeuvres will not significantly alter the regional military balance.
And both Moscow and Beijing remain wary of each other.
For Moscow there must be questions over China's long-term strategic goals, and for Beijing continuing doubts about Russia's reliability as an ally.
And, in the long run, this hardly looks like a stable relationship.
Russia approaches it from the perspective of a former and declining great power.
And while China is a country whose ambitions for the moment outstrip its actual power, that may not be the case for too much longer.