Once again, Vladimir Putin has resurrected a Cold War precedent.
Until last night, the Collective Security Treaty Organisation, a military alliance of ex-Soviet states, was a paper tiger. The body was widely seen as an instrument for projecting Russian influence inside the former USSR but not for doing anything practical.
Now it is mobilising for real, and with surprising capability, moving with speed to get a rapid response force out of the door.
The CSTO intervention in Kazakhstan has clear parallels with the Warsaw Pact invasions of Hungary and Czechoslovakia in 1956 and 1968.
Then, as now, a Moscow-led military alliance has intervened to put down an uprising in a neighbouring country that the Kremlin clearly feels lies within its rightful sphere of influence.
Then, as now, Moscow has taken its allies with it, an assertion of regional leadership that also provides some legitimising cover for the action.
But this is not an exercise in Soviet nostalgia.
Kazakhstan is the largest, wealthiest, and best educated country in central Asia. It shares an 4700-mile border with Russia, and the regime of former ruler Nursultan Nazarbayev, although by no means a mere vassal, was an important and reliable ally.
Going in to put down disorder there, Mr Putin has decided, is less risky than staying out.
There is also a principle at stake: one that well pre-dates the Soviet leaders to whom Mr Putin is often compared.
In 1849, the Habsburg empire asked Tsar Nicholas I to send an army to crush a nascent revolution in Hungary.
Half a century earlier, the monarchies of Russia, Austria and Prussia - and, to a point, Britain - had found common cause against revolutionary and Napoleonic France because autocratic monarchies could not allow one of their own to be overthrown.
The point is simple. Conservative autocracies must not be brought low by street uprisings. Not on Mr Putin's watch.
So it does not matter that, unlike the 2014 Maidan revolution that prompted a Russian annexation and invasion of Ukraine, there is nothing in the Kazakh uprising that could be called "pro-Western."
No one is running up the EU flag in Almaty. No one is threatening Russia's regional hegemony. It is about fuel prices, corruption, and frustration with an elite that has been in power too long.
We have seen this principle play out before.
In Belarus in 2020, leaders of the national uprising against Alexander Lukashenko's dictatorship explicitly reassured the Kremlin that its foreign policy interests were not at risk.
The Kremlin was unmoved, and looked on as Mr Lukashenko crushed the revolution with a brutality that Mr Putin has never dared try in Moscow.
Actually deploying forces carries much greater risks, of course.
Some have argued the deployment of airborne forces to Kazakhstan will have a delaying effect on Mr Putin's threatened invasion of Ukraine.
From the point of view of military practicalities, they may be right.
That doesn't mean Moscow has forgotten its conflict with Ukraine, or the grand confrontation with the West it believes is unfolding there.
Russian troops still remain stationed on Ukraine's border, poised for war.
Talks between Russia and the United States to avert that war will still go ahead this weekend.
And Mr Putin still firmly believes that Nato must be rolled back, and Ukraine brought back into alignment with Moscow. ally.