MANILA TRAINING CENTER, Iraq -- Hundreds of Christian men are picking up rifles for the first time at a former U.S. military facility in the hills of northeast Iraq and training to reclaim their towns from Islamic State militants who stormed the country last year. Fresh recruits to a new Iraqi Christian militia said their families were abandoned to militants by government forces last summer and they seek to create a force that will keep their towns and villages safe even after Islamic State is defeated. "I want to defend our own lands, with our own force," said Nasser Abdullah, 26 years old, who is helping lead younger recruits in training. Sunni neighbors in nearby villages, the recruits said, supported the Sunni extremists of Islamic State as militants seized one Christian village after another in the Nineveh plains, where Iraqi Christians and other minorities live. As Islamic State fighters advanced, Kurdish forces assigned to the region fled under attack, leaving exposed vulnerable communities. "Those who betrayed us won't be allowed to live among us," said Firas Metr, a 27-year-old electrician and recruit with no military experience. "We need to protect ourselves, now and in the future."

Some 30,000 Christians have since fled the Nineveh plains. Just one Christian town there, Al Qosh, and three smaller villages remain free. Across Iraq, more than 150,000 Christians have been displaced since Islamic State began its rampage, according to Iraqi Christian community leaders. More than 2,000 men have signed up to fight, but it wasn't clear whether they could afford to train them all. Organizers hope the U.S. will help. The U.S. National Defense Authorization Act, approved in December, names local security forces in Iraq as potential beneficiaries of as much as $1.6 billion to train and equip fighters against Islamic State. Those funds should support "local forces that are committed to protecting highly vulnerable ethnic and religious minority communities in the Nineveh Plain and elsewhere," said a statement accompanying the act.

Iraqi Christians, particularly Chaldean Catholics of ethnic Assyrian origin, have long ties with U.S. lawmakers through its large expatriate community. Former Democratic Sen. Carl Levin, who retired in December, helped include specific reference to the Nineveh area, which they hope will yield U.S. funding. U.S. officials familiar with the effort said the idea has been to include minority groups that could use assistance, especially after the siege of Yazidi families by Islamic State militants last summer in Iraq. Mr. Levin said this week he hoped the training program was successful but didn't know enough about it to comment further. On a recent Sunday, roughly 300 Christian recruits, toting duffel bags, left on a dozen buses bound for a training camp outside the city of Kirkuk. They sang and danced with the air of students en route to summer camp.

Local Christian politicians have tried for a decade to arm and train a Christian regional guard but faced resistance from Iraqi authorities. While under attack by Islamic State's predecessor, al Qaeda in Iraq, the Assyrian Christians got permission and funding for local watchmen but never the armed militias they hoped for. This month, that will change. "This is a fight to take back and come back to our land," said Yonadam Kanna, a parliamentarian with the Assyrian Democratic Movement, the political party leading the training. "It's as though our roots of thousands of years have been pulled out of the ground." Snubbed by the central government in Baghdad, party officials pressed their demands over the past weeks with the Kurdistan Regional Government, whose semiautonomous region in the north abuts the Nineveh plains. The Kurds offered the training facility outside Kirkuk, a base once run by the U.S. military to train Kurdish regional guards, Kurdish and Christian officials said.

About 500 recruits, mostly Assyrians, will be trained this month but it is uncertain who will fund and equip them in the long term. Christians here are divided about having their own militia. Patriarch Louis Sako, head of the Chaldean Catholic Church, which many Assyrians follow, has said he disapproves. The new militia is seen by some Iraqis as more evidence of how the country is fractured along sectarian and tribal lines, despite efforts by various sides to wage a unified battle against Islamic State. Prime Minister Haidar al-Abadi came into power last year under pressure to heal the rifts dividing Sunnis and Shiites, Arabs and Kurds, which worsened under his predecessor, Nouri al-Maliki. Mashaan al-Jabouri, a Sunni member of parliament, said a weak Shiite-led government hasn't been able to overcome the distrust among these groups. Mr. Abdullah, one of the Christian recruit leaders, was serving with the Peshmerga, the Kurdish regional force, in the Nineveh plains when Islamic State seized the city of Mosul in June. The Peshmerga guard land, including Christian towns, in northern territory contested between Kurdish and Iraqi authorities.

Mr. Abdullah said when he heard Peshmerga comrades had fled as Islamic State militants took Mosul, he recalled thinking: "I wouldn't want to defend a place that isn't mine either." He quit the next day. Months later, Mr. Abdullah signed up for a Christian militia that served as a trial run for the current effort. About 100 local men took up arms last summer to guard villages still free from Islamic State. At the training camp outside Kirkuk, Mr. Abdullah joined other ranking militiamen to coach the recruits. "They are excited, but they are nervous for sure," said Steven Yousef, 21 years old, as rows of men awaited their first roll call. Most have never seen an Islamic State militant, he said, or fired a gun. As many as half of Iraq's Christians are estimated to have fled over the past decade, and a second wave is bound for Istanbul, Beirut, and Amman, Christian community leaders said.

Residents of the Nineveh plains, home to such minority groups as Yazidis and ethnic Shabak, have for years felt vulnerable, living in the middle of a struggle between Iraqi and Kurdish authorities over control of the region. "No one has protected the minorities, and no one will in the future," said Kaldo Oghanna, an Assyrian party official who swapped his suit for military fatigues to oversee the first week of training. Assyrian party officials--who call their fledging force a battalion--say their goal is to retake Christian towns from Islamic State and police them independently until the dust settles. In Erbil, a Peshmerga spokesman said he understood from meetings with Christian officials that the militia would eventually work under the Peshmerga. Mr. Oghanna said there was no such agreement. Other party officials said they were open to incorporating trained units into a future national guard, but had doubts about its eventual deployment. Recruits said they wanted independence to protect their communities after expelling Islamic State.

Without financial support from the Iraqi, Kurdish or U.S. governments, the Christian militia has so far operated on donations, mostly from Assyrians abroad. Every recruit will get a rifle, Mr. Oghanna said, though the ones used in training are lent by Kurdish camp authorities, along with machine guns and mortars. Several Americans were helping train the young men. They said they had served in the U.S. military and were volunteering through a nonprofit organization they declined to name. They wouldn't talk about their mission or background, saying they needed to protect their identities from Islamic State, also known as ISIS and ISIL. One of the American trainers, 28 years old, said U.S. officials in Erbil were briefed on the Christian militia but weren't involved. U.S. officials didn't respond to requests for comment.

"The Americans want to stay away from this because their view is, if you train the Christians, you're starting some crazy religious war," he said. "Well, ISIS beat you to it."

Ali A. Nabhan contributed to this article.