BAGHDAD — With wooden crosses around their necks and others tattooed on their arms, several dozen Iraqi Christians are training to recapture their homes overrun by ISIS militants.

A year ago, ISIS launched a fierce offensive in northern Iraq, quickly capturing second city Mosul with its large Christian minority, and Christian-populated areas in the surrounding Nineveh province.

Residents were given the choice of converting to Islam, paying a tax to continue practicing their faith, or death. Thousands fled, but some want to fight back, and are now training at a military base near the Baghdad airport.

They have paramilitary fighters instructing them on rifles and the basics of combat maneuvers, but they are vocal in their Christianity on parade, chanting Ya Mariam (O Mary) in cadence as they march in a salute to the mother of Jesus.

“We heard that the Christians had an opportunity for jihad, and we all came and volunteered,” said 17-year-old Chaldean Christian Frank Samir.

“Our children are dying; our Christian families were displaced. How do we ourselves accept that people say the Christians are not fighting? On the contrary, we want to fight everywhere,” he said.

Samir is from Baghdad, but most of the Christians in the “Babylon Battalions” unit are from Mosul.

Both Christian and Muslim religious symbols are displayed at the training area. These include a large cross affixed to a concrete blast wall and banners reading “God is greatest” and “There is no god but God,” the first part of the Muslim testament of faith.

“The main aim of forming our forces is the liberation of Mosul,” said Rayan al-Kaldani, the secretary general of the Babylon Battalions.

According to Kaldani, the Christians fight under the command of Abu Mahdi al-Mohandis, one of the top commanders in the “Popular Mobilization” forces, an umbrella organization mainly made up of Shi’a fighters.