"There are a lot of corpses of women and children," the rebel commander said. "It has a Malaysia Airlines logo on it, they say." He seemed to seek advice. "That means it was carrying spies," came the response. "[Expletive] them, got it?" So spoke one of the most influential and well-connected Cossacks in Russia.

Ukrainian officials yesterday released audio recordings purportedly between separatist forces who shot Malaysian Air MA17 out of the sky and their Russian-affiliated advisors. While many of the rebels and Russians on the as-yet unverified radio intercepts express uncertainty and regret, one voice near the end of the recording is clear and unrepentant. "They shouldn't be [expletive] flying," the man says, after cursing the downed plane's occupants as spies. "There's a war going on."

Ukraine says that voice belongs to Nikolai Ivanovich Kozitsyn, for decades the leader and public face of the Don Cossacks, who in recent months has become notorious in the international community for stoking the fires of pro-Russian nationalism and coordinating dirty tricks in the conflict there.

Kozitsyn's position of privilege and authority among the pro-Russian rebels who have seized parts of Eastern Ukraine in recent months is relatively well-known. But if yesterday's recording is authentic, it may indicate a new stage of violent militancy for the former Russian prison guard and highly decorated public figure, who's been close to Russian leadership since Yeltsin, and who has spent several decades as the Cossacks' "ataman" trying to rehabilitate the group's public image and mend broken fences with groups, like Jews, whom the Cossacks once victimized.

Shortly after the Soviet Union's breakup, Kozitsyn (whose first name is also sometimes rendered as Mykola) bargained for influence in the fledgling Russian government's battles with Chechen separatists, eventually throwing his support behind Russian President Boris Yeltsin in exchange for political clout. "Like all citizens of Russia, I was wounded by socialism," the Cossack told the New York Times in 1996. "We support President Yeltsin." He then touted his own military prowess:

...at his headquarters, Mr. Kozitsyn proudly pulled out a 1989 picture of himself in the trenches of the Transdniester region, a breakaway ethnic Russian area of Moldova.

"We captured a tank from the Romanians," he said, referring derisively to the predominant ethnic group in Moldova, a former Soviet republic that is now independent.

Mr. Kozitsyn professed no interest in fighting the Chechens in southern Russia. But fear of the Muslim Chechens has helped fuel the Cossack resurgence, and Cossacks in and around Chechnya have argued for a firm Russian hand.

By the late '90s, Kozitsyn had emerged as a public spokesman for the plight of "oppressed" Cossacks, taking his case for "historical justice" and "what our forefathers had" to any journalist who would listen.

But Kozitsyn's power was always based on a militant, nativist pro-Russianism. In 2002, he made headlines after calling for stricter immigration controls in the Federation, especially against Armenians. "Let them go to Armenia, Georgia, and Meskhetia," he said. "Let them rebuild their towns there. How long will they milk the Russians?"

By 2004, his power in the Don region of Russia, just east of the Ukrainian border was unparalleled. The Don Cossacks had set up six military academies for young cadets; they patrolled the streets of numerous cities in the region, welcome vigilante crusaders. "Everyone in Russia wants to be a Cossack," he bragged. "It's become fashionable."

The Cossack resurgence made some local Jews nervous, and Kozitsyn took pains to court them in an interview with the Jewish Telegraph Agency, noting "that he 'had a lot of Jewish teachers' growing up":

Kozitsyn says the Don Cossacks "understand" Russian Jews, because both groups suffered the same oppression under Soviet rule. He neglects to mention the historic animosity between Cossack and Jew in the Russian Pale of Settlement, nor does he bring up the Cossacks who welcomed the Nazi invaders in 1941 as "liberators" from their communist overlords.

But PR took a backseat to strategic jockeying and weekend warrioring for Kozitsyn. When rumblings began in Ukraine last year, his forces were well-poised to cross the border into Luhansk and Donetsk, ready to support Russian aims—the culmination of 20 years' work with Moscow to further its strategic and territorial goals in disputed territories.

Concern over his stature seems to have grown in the leadup to Thursday's deadly attack. Just last Saturday, the European Union had identified Kozitsyn as a key militant leader and slapped him with sanctions, including a freeze on European-held assets and a ban on his travel.

That move came a month after the Ukrainian government blamed Kozitsyn for coordinating the kidnappings in April of nine international observers from the Organization for Security and Cooperation in Europe, a claim backed up by reporting in the German weekly Der Spiegel. In connection with those allegations, Ukraine's state security service released a video in early June including alleged calls between rebels and Kozitsyn in which the Cossack leader appears to give the separatist forces tactical orders and discuss equipping them with military-grade weaponry.

The Ukrainian transcript of one purported call between Kozitsyn and a "terrorist" appears to show the ataman giving orders to destroy or secure a fuel depot:

Kozitsyn: They say that there is a fuel storage not far from you.

Terrorist: The army one?

Kozitsyn: Well, yes. We need to make it disappear.

Terrorist: I got you.

Later, Kozitsyn allegedly gives the following rousing advice to a rebel leader:

Kozitsyn: God bless you! Sergey, fuck them on the left and right. Do not stop! Got it? I want to see the vengeance fire! Listen, you need to reward everyone who either shot down a helicopter or burned an APC with a medal.

Terrorist: Will be done, Mykola Ivanovych, got it.

Kozitsyn: That's all. And I'm waiting for "big boom."

Of course, these are motivated accounts coming from Kiev's fledgling government, which has a clear interest in linking the rebels it's fighting to Russian President Vladimir Putin through allies like Kozitsyn. But The Don Cossacks' home page includes an order from Kozitsyn to form a Cossack National Guard and fight the Ukrainian nationalist movement:

In the south-east of Ukraine are bloody battles with the occupation forces, consisting not only of the members of the Kiev Maidan and boys from western Ukraine, but also mercenaries from Europe and America... the Cossack Army National Guard must be closely involved in the termination of this bloody war, the destruction of the living and the technical strength of the enemy, in the liberation of the southeast of Ukraine from the Nazis. I urge all the Cossacks with honor and conscience to stand up for his brothers in blood.

Whatever his level of involvement in the Malaysia Airlines shootdown and the conflict that proceeded it, Kozitsyn is likely to stake out a prominent role for himself in the future of Eastern Ukraine—which means officials in Washington, Moscow, Kiev, and Europe will have to deal with him somehow. As he told JTA a decade ago: "There are no bad people, only bad leaders."