It must rank as one of the world's most daunting jobs: tackling corruption in Ukraine's military. But with support from the president, a patriotic volunteer unit and a polygraph test, one man thinks he has the answer.

David Arakhamia knew the corruption he would unearth in Ukraine's notoriously graft-ridden ministry of defence would be bad, but he was still shocked.

"It is huge," he said. "From what we can tell, not one single deal has been free from corruption. The amounts range from 10 to 90 percent."

He described typical methods for skimming money when buying defence gear. First, increase the price and pocket the difference. Then buy a cheaper version.

And if you really want to cash in, put some of the goods in a warehouse and blow it up, blaming the enemy and selling the rest on the black market.

"That happened a couple of months ago. A warehouse with a brand-new load of supplies got mysteriously hit by a stray missile," he said.

For Ukraine's desperately under-equipped troops -- fighting a vicious war against Russian-backed rebels in the east -- such corruption can be lethal.

That's why President Petro Poroshenko has made the ministry of defence the test case for his plans to root out graft.

He empowered Arakhamia and his anti-graft squad of 11 people known as "volunteers" -- referring to their background as helpers organising supplies for the troops through private channels -- to stick their noses into the ministry's books.

"We have the power to go anywhere and if anyone blocks us, we go straight to the president," Arakhamia said.

If successful, he hopes the pilot project could provide a blueprint for cleaning up the rest of the government.

- Polygraph tests -

The first challenge for Arakhamia -- a Georgian IT executive whose family fled to Ukraine during civil war in the 1990s -- was how to select an unimpeachable team.

Arakhamia subjected candidates to a four-and-a-half hour polygraph exam designed to test their patriotism and whether they had ever taken or paid a bribe.

A quarter of volunteers failed.

His final selections got to work in mid-November, figuring out how to clean up and streamline deliveries of weapons, food and uniforms.

Heads are already rolling. A fortnight ago, the ministry's chief procurement officer Oleksandr Zrazhevskiy was arrested. Officers found $420,000 in his safe.

"That was just pocket money," said Arakhamia. "He wore a $200,000 watch to work."

The head of the ministry's health department is also under investigation, along with several lower officials.

The next step is polygraph tests for everyone who comes under suspicion.

"I'm expecting to see a huge number of retirements in the coming weeks," he said.

- Troops begging for gas -

Corruption has sharpened the already chronic shortages faced by Ukraine's troops, leaving them heavily dependent on donations.

When Anton Tarasov, a volunteer with the VS Ukraine-World charity, first encountered one artillery division near the frontline in rebel-held Lugansk "they were stopping cars on the side of the road, begging for gasoline to run their generator".

"They showed me their camp. Not one of them had a sleeping bag, let alone a tent."

Volunteers supplied them with warm clothes, diesel generators and boots.

An IT company even donated four tablet computers loaded with hacked military targeting software so they would no longer have to get their orders by mobile phone and plot trajectories with a map and compass.

Corruption in official channels is the biggest challenge for volunteers and international donors.

"A significant amount of goods don't get to the fighters -- up to 30 percent when it was really bad at the beginning," said Olena Masorina, the charity's leader.

"Commanders take it from us and sell it on the Internet."

In one case, she says, 10,000 euros' worth of flak jackets and clothing never reached its destination.

- 'Not for sale' -

It's a problem with which Arakhamia -- who set up the biggest crowd-funding site for donations to the military before taking on his new job at the ministry -- is depressingly familiar.

"We had to start engraving 'Not for sale: donated by the people' into thermal-imaging goggles," he said.

Arakhamia knows all this is making him enemies.

"I don't care. There are soldiers in the front -- we are the soldiers in the back.

"The difference is they know who their enemy is. We don't -- we have to hunt them out."