For decades, Russia conducted military exercises, in large part, to prepare for attacks by or on its neighbour, China.

In less than a fortnight, Russia will hold joint military exercises with its former bitter foe in one of the most awesome displays of military force the world has ever seen.

Russia and China – who for years sniped at each other across their shared border – will from September 11 stage war games involving a staggering 300,000 Russian troops, 1000 aircraft, 900 tanks and two naval fleets. It will also include units, helicopters and about 3200 troops from China’s People’s Liberation Army (PLA) and the Mongolian army.

The Vostok-2018 exercise is easily the biggest simulation of warfare to take place in the post-Soviet era and the biggest in Russia since its mammoth 1981 Zapad (west) exercise.

Watch the Zapad 81 war games

It prompted a NATO spokesman to warn of “a more assertive Russia” and of “Russia’s focus on exercising large-scale conflict”.

Alexey Muraviev, an associate professor of national security and strategic studies at Curtin University, agreed it’s a mighty and unprecedented show of strength.

“It’s about one third of the whole [Russian] military,” he said. “It’s effectively amassing and using an army the size of United Kingdom’s or France’s.”

But Dr Muraviev said the move doesn’t necessarily signal the birth of a Cold War-style alliance between Moscow and Beijing, creating a giant, menacing superpower. It is more nuanced than that.

“The first key point is to ensure China doesn’t feel threatened about Russia’s war games in the far east … Russia includes China simply so the Chinese don’t get worried,” he said.

“China and Russia need to protect each other’s back. In the past they confronted each other, but now they don’t want to be in a position where they need to consider each other a threat.”

And that sense of harmony leads to the second rationale. Dr Muraviev said it’s a show of solidarity in the face of increased tension with the US and Europe.

“Russia wants to showcase its grown, special defence relationship with China, in light of its heightened military and political tensions with NATO and the US,” he said.

“They are both on the same page in that both of them want to challenge US supremacy.”

There has been a growing “strategic intimacy” between the two nations since the early 1990s, Dr Muraviev said, but this may have gathered pace under the presidency of Donald Trump.

The upside for China is also gaining combat experience alongside a top-notch fighting unit like the Red Army.

“The PLA has much state support and a huge budget, but lacks combat experience. It hasn’t really had any relevant combat experience since the Vietnam War.”

“Remember that both countries are the targets of US economic sanctions.” Photo: Getty

Professor Mark Edele, a Russia and Soviet historian at the University of Melbourne, believes what is feeding the new friendship is also a shared enmity for the US.

“What drives them together is an opposition to the US, against generally what they perceive as a hegemonic power [in the US],” Professor Edele says. “Remember that both countries are the targets of US economic sanctions.”

Professor Edele believes it may also be a recognition by Russia that it needs to cosy up to China because the latter has clearly evolved into the superior economic power.

But Russia’s motives may also be more cynical, he says: not only does such a huge show of force feed into the general narrative of President Vladimir Putin’s military muscle-flexing, but could also help distract from problems on the home front.

“For Putin showing strength is all important. He always wants to punch above his weight internationally and at the moment, that’s all his government has going for it.

“Russia’s economy is still struggling and still hasn’t managed to diversify the economy beyond the resources industry. His [Putin’s] attempts at reforming the age pension in Russia has also stirred up a huge backlash – a bit of sabre-rattling always comes in handy in those situations.”