The frontline separating these pro-Russian rebel fighters from Ukrainian army troops in this troubled region lies only 30 kilometres (20 miles) away.
But the enemy the Cossacks fear most is the enemy within -- the separatist leaders of the self-declared Luhansk People's Republic (LNR) who they refuse to obey.
"We're under the orders of our Russian brothers of the Great Army of the Don Cossacks. We don't recognise the authority of the LNR," said the soldier.
In this small town some 30 kilometres of the separatist bastion of Luhansk, a handful of well-armed and somewhat nervy Cossacks man a roadblock adorned with their blue, yellow and red flag inscribed with the words "For faith, the Don and the Fatherland."
- No idle threat -
Elite horsemen in the Tsarist army in the old days, frontier Cossack communities were set up over the centuries across the former Russian empire, with the Don Cossacks primarily claiming lands stretching from southwest Russia to Ukraine's eastern Donbass region.
Now they claim to be defending the interests of Russia abroad while fighting for their fierce brand of reactionary nationalism.
Igor Plotnitsky, head of the Luhansk rebels battling the Kiev government, set an April 4 deadline for the Cossacks to either join the LNR's military wing, hand over their weapons -- or be outlawed.
The deadline was no idle threat.
Faced by blatant Cossack disobedience, the Luhansk rebels have hit back hard against the militiamen in recent weeks.
On March 30, Cossacks were attacked and disarmed in the neighbouring town of Petrovsk in an operation in which several people died.
A month earlier a leading local Cossack Ataman, or leader, was arrested nearby in a deadly raid.
In January the Cossack mayor of Pervomaisk, Yevgeny Ischenko, was shot dead by unknown gunman while a local warlord allied to another group of Cossacks, Alexander Bednov, known by his nickname "Batman", died along with six bodyguards when his armoured car was hit by an anti-tank missile in an ambush.
AFP reporters noted that some 20 kilometres north of Perevalsk, the town of Stakhanov, which is under Cossack control, is on a state of alert with foreigners unable to enter or leave without a pass and a military escort, an apparently unique security situation in the area.
- 'We want more freedom' -
The deputy mayor of the town -- that now houses some 70,000 people -- does not hide the fact that relations with the Luhansk rebels are tense.
"Plotnitsky said that there is no question of autonomous Cossack territories," Vasily Kiselyov, 39, told AFP.
"He wants a strong central power. That is what we are opposed to. We want more freedom."
Sitting in his office under the portrait of a local Cossack leader, Kiselyov called for Plotnitsky to be ditched after accusing him and his cronies of pilfering aid deliveries coming from Russia and siphoning off coal supplies.
"We didn't get rid of the Ukrainian oligarchs just to replace them with a new bunch," he said.
More than just the allegations of corruption -- accusations that the Lugansk rebels fling right back at them -- the Cossacks lambast the separatist leaders for signing a Russian-backed ceasefire deal with the Ukraine government that they say they do not recognise.
The problem of the renegade Cossacks is a major headache for the rebel chiefs in the Luhansk region -- the smaller of two separatist enclaves -- and shows the splintered loyalties of some of the rebel groups in the east.
Now as the fighting has died down along the frontline with Ukrainian forces since the February truce deal, the insurgent leadership has had more opportunity to refocus its attention on bringing the unruly Cossacks into line.
But that does not seem to be worrying the Cossack deputy mayor, as he sits under an icon of the Virgin Mary and Stalin.
"That was a wise man," he said of the Soviet tyrant.
"Maybe even if he was sometimes a bit too tough."