Readers may not know the name Sergei Skripal, but the name Anna Chapman will ring some bells. Chapman became the public face of a Russian spy ring in the US that got caught almost eight years ago, and which may have been attempting to penetrate the Obama administration and/or Hillary Clinton’s donor network. It didn’t take long for the US to negotiate a swap with Russia, trading the ten spies for four Western intelligence moles that had been imprisoned in Russia.

That’s where Sergei Skripal comes in — and why he may have been taken out:

A man who is critically ill after being exposed to an unknown substance in Wiltshire is a Russian national convicted of spying for Britain, the BBC understands.

Sergei Skripal, who is 66, was granted refuge in the UK following a “spy swap” between the US and Russia in 2010.

Police declared a major incident on Sunday after a man and a woman were reported ill in a shopping centre in Salisbury.

Both Skripal and the unidentified woman, described as in her thirties, were found unconscious on a bench. Police declared it a “major incident” and sent in a hazmat team, and the hospital emergency room was cleared out while the two were being treated:

Temporary Assistant Chief Constable Craig Holden said: “The pair, who we believe are known to each other, did not have any visible injuries and were taken to Salisbury District Hospital.

“They are currently being treated for suspected exposure to an unknown substance. Both are currently in a critical condition in intensive care.[“] …

A PHE spokesman said: “PHE understands that those exposed to the substances have been decontaminated, as is standard practice in situations like this.

“Scientists from PHE’s Centre for Radiation, Chemical and Environmental Hazards will continue to assist the response and review information as it becomes available.”

This may sound familiar to those who remember Alexander Litvinenko’s death in 2006. Litvinenko was another former Russian spy turned Vladimir Putin critic who got a fatal dose of polonium-210. It took several days for Litvinenko to die, during which he publicly blamed Putin for ordering the hit:

Former Russian spy Alexander Litvinenko was fatally poisoned by a radioactive substance, traces of which were found in his urine, at his home and at a London restaurant and hotel he visited the day he became ill, according to the British health department. It called the case “unprecedented” in Britain.

Authorities closed the restaurant and sealed off part of the hotel Friday as part of an emergency effort to trace the substance, polonium 210, and ensure that it does not harm other people. Litvinenko would have eaten, inhaled or received it through a wound, according to Pat Troop, chief executive of Britain’s Health Protection Agency.

Coming after the mysterious poisoning of another prominent opponent of the Kremlin, Ukrainian politician Viktor Yushchenko, the death provoked accusations that Russia continues to use Cold War-style tactics to eliminate critics abroad. London was the scene of the 1978 assassination of a Bulgarian dissident who was killed by a jab from a umbrella tip bearing the toxin ricin.

Litvinenko blamed the Kremlin shortly before he died, according to friends and family members. “As I lie here I can distinctly hear the beating of wings of the angel of death,” Litvinenko, 43, said in a dictated statement, according to friend Alex Goldfarb, who met reporters while accompanied by Litvinenko’s tearful father.

“You may succeed in silencing one man but the howl of protest from around the world will reverberate, Mr. Putin, in your ears for the rest of your life,” the statement said. “May God forgive you for what you have done, not only to me but to beloved Russia and its people.”

At that time, Putin denied having anything to do with Litvinenko’s murder, although polonium-210 is a substance that is so rare and dangerous that it remains mainly in the control of governments. Putin was more voluble at the time of the Chapman swap four years later, promising retribution for all “traitors,” and warning intelligence agents that they knew what was coming their way:

Prime Minister Vladimir Putin, himself a former KGB spy, greeted them as heroes. He said traitors came to a bad end, and the informer would be left to the mercy of his own kind.

“The special services live by their own laws and everyone knows what these laws are,” he said shortly after the swap.

That seemed to have been intended for former intelligence officer Colonel Shcherbakov, who reportedly exposed the ring to the US and got out of Russia just days ahead of their arrests. That warning could easily apply to Skripal too, though, who also acted as a mole for the US. Putin has a long memory, and no compunctions about getting even in spectacular fashion, as the Litvinenko murder demonstrated. Wherever Shcherbakov is now, you can bet he’s gotten the message. So have any others who might believe they can escape to the West — and that’s precisely the point of high-profile assassinations.

Let this be a lesson to the West that Putin is no mere politician looking for an edge. He’s playing for keeps, trying to re-establish Russian imperialism sowing discord among those he sees as enemies. We have spent years underestimating the threat of Putin’s oligarchy and hostility, a failing of three successive US presidencies. This administration needs to get past the personal issues involved in Russian policy and start hardening the US against the intelligence and military threats Putin represents.