In a bunker below the fiercely contested city of Bakhmut, a jihadi commander with a half a million-dollar Russian bounty on his head, joins his men in prayer.

Of the allies Ukraine has gathered in its war with Russia, among the most shadowy and deadly are the Chechens.

They are some of Vladimir Putin’s oldest enemies and among the hardest to film up close.

Read more: Chilling moment Russian soldiers scour Ukrainian orphanage for children

They are all marked men, wanted by Russia. Their movements are shrouded in secrecy. But Sky News gained access to their secret base near the frontline in one of Ukraine’s most savage battles.

During the time we spent filming them they shared insights into their foes that are worth listening to in the West.

We drove in fast on back roads to evade Russian spotters calling in artillery strikes. As we entered Bakhmut we passed gutted buildings and gaping craters, the sound of shelling was close and regular.

Ukraine war: Chechen leader says he will send teenage sons to fight in Ukraine

LGBT persecution in Chechnya: Bisexual woman beaten, drugged and exorcised

Mo Salah given honorary citizenship by Chechen leader

Inside the bunker we met some of the longest serving veterans of this war. The Chechen Sheikh Mansour Battalion has been fighting Russia in Ukraine since 2014. Their enemy’s tactics haven’t changed since this war began, they say.

“They’re sending forward troops like cattle for slaughter,” Chechen fighter Idris told us. “Leaving the ground covered with corpses. They do it every day they have no pity for their own people.”

It is the same kind of fighting Russia used in their homeland in the 1990s. From safe cover, commanders send conscripts in waves hoping to grind down their enemy with little care for their men.

Chechens have been fighting for an independent country since the collapse of the Soviet Union.

After victory in the first Chechen war they were defeated by Russia, and Vladimir Putin installed a puppet leader, Ramzan Kadyrov, propping him up with billions of dollars in support.

He combines brutal repression with self-promotion on social media that veers from the sinister to the preposterous.

His Chechen forces fight on the side of Russia in this war. His Chechen enemies on the other. The conflict has given Chechen separatists a new arena for their struggle against their enemy.

Commander Muslim Cheberloyevskii leads the Sheikh Mansour battalion, one of their most active fighting units. He gives very few interviews but made an exception for Sky News. Before joining his men in Bakhmut we spoke to him on a video link to his secret location elsewhere in Ukraine.

“There can be no options here,” he said. “Russia must lose, and it must end there. If we do not defend Ukraine today, everyone will lose.”

The man who has fought Putin’s forces longer possibly than any other commander, used the interview to warn policy makers in the West they are not doing enough to defeat him.

“I think more support is necessary. The West provides support by portions, they are limited. Munitions are quickly used, they are not enough on the battlefield. If we had more, we could win quicker.”

In the bunker under Bakhmut there was the same message. Base commander Mansour has spent two decades fighting the Russians, eight of them spent in jail where he was tortured.

“I have no pity for them at all,” he said of his enemy. “Because God gave everyone a brain for thinking. If he’s not thinking he shouldn’t walk on the earth, he belongs below the ground.”

The Chechens have been fighting the Russians in their mountainous Caucasian homeland on and off since the days of Peter the Great in the eighteenth century. They pride themselves on their fighting spirit and warlike ability. As Muslims many of them regard their struggle with Moscow to be a jihad, or holy war.

When the Soviet Union collapsed, they fought in the mid-1990s to try and win independence and defeated Russian forces despite their enemy’s superior numbers and weapons.

Under Vladimir Putin, Russian forces retook control of Chechnya in the second Chechen war. The Russians used a pulverise and conquer strategy reducing most of the capital Grozny to rubble. They have applied the same tactics in Ukraine in cities like Mariupol.

Chechnya is now ruled by Ramzan Kadyrov, Chechen separatist turned Russian puppet, and his clan. He has used billions of dollars in Russian aid to fund a security state noted for brutal repression and over the top social media propaganda.

After years spread far and wide, Chechen freedom fighters are regrouping in Ukraine drawing in supporters from across Europe, Asia and the Middle East. When the war ends there, they hope to take their fight to Russia back home and win back their homeland.

And he warned Western leaders not to fall for Putin’s enticements to negotiate an end to this war.

“Even when they agree to negotiate and sign some documents, they do not follow them, they act treacherously.”

They are a sabotage unit, using weapons, some improvised, to strike the enemy in their trenches. Commander Mansour showed us a homemade rocket propelled grenade fashioned from a fire extinguisher packed with plastic explosives.

On a work bench nearby a suicide vest was being constructed. They wear them should Russians take them prisoner. The base is mined, they said, to blow up if the enemy should overrun it.

In an outbuilding, Deputy Commander Mansour showed off what he called his “Devil’s machine”, a rocket launcher improvised to fire converted mine clearance shells.

On his phone he shared video of the device in action at night. A fiery launch followed by a pause then a huge explosion in the distance lighting up the sky with a mushroom cloud of fire. The fighters shout Allahu Akbar: God is great.

They fight here hoping one day to take their holy war back to their homeland. Kadyrov is unpopular but well-funded and protected by thousands of well-armed security forces. When the war is over though they say they will continue fighting Russia, hoping to topple him.

Asadullah, a Ukrainian who converted to Islam and joined the battalion speaks for many of them.

“If today the war ends in Ukraine, and we win, for us it will not end,” he said.

“We will fight till that time when we destroy that empire of evil totally.”

For now though, that is a very long way off. We left their bunker and drove again at speed out of Bakhmut to a backdrop of artillery fire. Their enemy is destroying another Ukrainian city block by block in a grinding war of attrition no one looks close to winning.

Related posts:

The sound of gunfire reverberated around us – with Afghans desperate to get out of Kabul Taliban declares ‘amnesty’ in Afghanistan and urges women to join government Thousands evacuated as wildfire races through forests near French Riviera Baby-faced dictator to nuclear hard man: A decade of Kim Jong-Un Five children killed in bouncy castle tragedy are named – as families pay tribute US warns any movement of Russian military forces across Ukraine’s border will be met with ‘severe response’ What impact will Russia’s decision to cut off gas to Poland and Bulgaria have on Europe and the UK? Travis Scott set to headline Brazil festival a day after first anniversary of Astroworld crush Ukraine’s World Cup challenge captivated its citizens briefly – but the war matters more UK pledges to send missiles to Ukraine as Russia warns of expanded conflict Putin has ‘no regrets’ over war in Ukraine and warns a clash with NATO could lead to ‘global catastrophe’ Far from the glitz of the Qatar World Cup a migrant worker’s family grieves