Since Islamic State militants declared a "caliphate" last year in parts of Iraq and Syria, thousands of Westerners have traveled there to join the battle.
But one American man told VOA he has joined the fight, not for the Islamic State jihadist group, but against it.
"I am in Iraq helping to raise a Christian army to fight ISIS," declared Matthew VanDyke in a statement on Twitter this week.
VanDyke is a bearded, blue-eyed Baltimore native with a slender build and a master's degree in security studies from Georgetown University. He has formed what he calls the Sons of Liberty International, or SOLI, a nonprofit group that is helping to train a militia made up of Assyrian Christians, whose homeland in northern Iraq has come under attack by Islamic State militants.
The militia, the Ninevah Plains Protection Units, or NPU, is one of several small groups of Christian fighters trying to defend vulnerable locals against the Islamic State group, which has carried out mass executions and expulsions of religious minorities.
The jihadi onslaught against the ancient Iraqi Christian community is part of what prompted VanDyke to go to Iraq in early December and join the fight against the Islamic State group.
"They've suffered greatly under ISIS," VanDyke told VOA via Skype from the northern Iraqi town of Irbil. "There's tens of thousands of Christian refugees and the population of Christians in Iraq is severely threatened."
VOA was not able to confirm VanDyke's location.
"A lot of them have left and have become refugees and will not return to their homes. And if the Christians cannot demonstrate that they're able to secure their own lands, Christianity will be wiped out," he said.
According to VanDyke, the best way to stop the onslaught is to equip locals to protect themselves. To do that, he is recruiting U.S. combat veterans to come to offer specialized training to the Assyrian fighters.
So far, Vandyke said five military vets have volunteered to help train the NPU.
"And it's going quite well," VanDyke said. "We ran a covert training camp north of Mosul for about a month."
"The results were very positive. I have observed the Iraqi army and the Afghan army in the past, and these fighters far surpassed them in their motivation and morale and talents and how quickly they learned and how seriously they take things," he said.
Kaldo Ramzi, an official with the NPU, confirmed to VOA that VanDyke and the Sons of Liberty International have helped provide basic training to about 500 fighters that make up the Assyrian militia.
Ramzi said for now, the NPU was focused on protecting lands not yet taken by the Islamic State militants. But once the group receives more training, funding, weapons and fighters, he said it planned go on the offensive to retake Assyrian towns captured by the extremists.
VanDyke and Ramzi even claimed to have met with U.S. State Department officials at a consulate in Iraq, who, they said, have given the NPU and its coordination with SOLI their full verbal support.
When contacted by VOA, a State Department official refused to confirm such a meeting.
"American civilians who may have traveled to Iraq to take part in military activities are not part of the United States government effort in Iraq," the official said.
"As our travel warning indicates, we have been clear that travel to Iraq remains very dangerous and that we do not endorse nonessential travel to Iraq by private U.S. citizens," the official added.
The NPU is trying to coordinate its efforts with at least some other local groups, including the Kurdish Peshmerga fighting force that is also battling Islamic State militants. Some of the NPU training camps have been held at Peshmerga bases, for instance, according to VanDyke and Ramzi.
But while the Peshmerga, backed by U.S.-led airstrikes, has had some success in retaking Kurdish areas from the Islamic State group, the paramilitary group has been hesitant to expand its efforts to other non-Kurdish territory captured by the Islamists, leaving many Assyrians desperate for help.
"For over six months, neither the Kurds nor the U.S. have lifted a finger to liberate towns, like [the Assyrian city of] Qaraqosh, which are a 10 minute drive from Kurdish front lines," said Michael Knights, an Iraq security specialist at the .
Other small groups of sectarian fighters are also interested only in defending their own territory, leaving no single unified anti-Islamic State fighting force and making the conflict a necessarily sectarian battle.