For decades China has been considered by Russia as one of its potential threats.
Russia's Vostok-2018 (East-2018) drills, which run until Monday, are taking place in Siberia and in waters off Russia's eastern coast, involving 300,000 troops, over 1,000 military aircraft and two naval fleets.
Chinese media reports have stated that 3,200 Chinese soldiers and 30 aircraft are also participating.
The wargames are taking place at a time of heightened tension between the West and Russia, and NATO has said it will monitor the exercise closely, as will the United States which has a strong military presence in the Asia-Pacific region.
But Moscow insists that they're just a regular annual test of the combat preparedness of its troops, and President Vladimir Putin has underlined that Russia does not have any aggressive intent..
What is notable is China's scaled up involvement; for decades Beijing had been considered by Russia as a potential threat.
China's People's Liberation Army has conducted military exercises in the past with Russia but never on such a scale and Chinese official media are trumpeting a deepening strategic partnership.
For the first time the media are openly highlighting that China’s partnership with Russia is intended to challenge the hegemonic role of the United States in the international system.
Meanwhile, experts debate whether the drills are a routine military affair to hone tactical cooperation in battle - or a not-so-subtle wink to "external enemies."
Russia is obviously flexing its muscles: it's about showing it's a global military power able to fight in far-off Syria and if the US ratchets up the sanctions it can always pivot towards China.
For China it's a much more subdued affair, a political analyst at the Hudson Institute, said.
"If you look at Chinese TV reports, they are showing how Xi Jinping at the economic forum in Vladivostok, talking about building infrastructure in the region, and putting much less emphasis on military drills. If they mention it, it's much more focused on keeping peace in the region. China doesn't want to be seen in an axis with Russia against the USA and the West," Jonas Parello-Plesner said.
And China is expected to learn a lot from a Russian military currently fighting in Syria - its own Peoples' Liberation Army has not been in an armed conflict since its last war with Vietnam in the late 1970s.