BAGHDAD—Surrounded by a blast wall topped with razor-sharp concertina wire, Our Lady of Salvation Church in downtown Baghdad resembles a fortress more than a sanctuary. Despite the fortifications, however, those who worship there are feeling more vulnerable than ever.
An appeal for help in guarding the Syriac Catholic Church this month brought no volunteers. A ragtag trio of armed men protects the churchyard. At Mass, guards patted down worshipers and checked their belongings for concealed weapons and explosives. Only a few dozen people occupied the pews, the wan echo of their voices lost in the vast nave where hundreds used to worship each week.
As Sunni militants of the Islamic State of Iraq and al-Sham, or ISIS, sweep through the country, the church's small congregation and makeshift defenders highlight the precarious condition of Iraq's Christian community. The community's ranks have shrunk by half in the past decade, as the devout flee the sectarian violence that has become a hallmark of post-Saddam Hussein Iraq.
One man at the church said that the country's largest religious communities—Sunni Muslims and Shiites—have often been too busy fighting each other to hunt Christians, but it is different this time.
"Now all these terrorists are here from across the Middle East, and they want to cleanse the Christians," said a 35-year-old armed guard at a checkpoint outside the church's main entrance. "The youth have left. There's no one left to defend the church, and if I had the chance, I'd leave, too."
In 2010, the congregation had a taste of the perils that possibly lay ahead. At least 58 people were killed when ISIS militants attacked the church and took more than 100 hostages.
While the members of Our Lady of Salvation worry that they will again be targeted in a sectarian attack, other Iraqi Christians are simply trying to avoid being caught in the tightening vise of extremist Sunni fighters and their foes.
On Tuesday, Syriac Catholics were among those fleeing the northern town of Qaraqosh as clashes raged between ISIS and Kurdish Peshmerga forces, residents said. ISIS mortars intended for the Peshmerga hit Qaraqosh, triggering the exodus of most of the 50,000 residents to Iraq's autonomous Kurdistan region and its capital, Erbil.
A small fighting force stayed behind in Qaraqosh to defend its religious sites, some dating to the eighth century. The Iraqi military was stretched too thin to help, said Ammar To'ma, a member of parliament's security and defense committee.
"No one is left in the village," said a teacher from Qaraqosh, who escaped to Erbil on Wednesday. "It was total chaos."
Increasingly, Christians risk becoming collateral damage in the main sectarian battle, said Bassim Bello, the mayor of nearby Tilkif.
"The Christians are the weakest chain in Iraq's society, and we've always warned that we will be the victims of any fighting," Mr. Bello said.
In Baghdad on Tuesday, Yonadam Kanna, a member of parliament and the leader of the main Christian party,the Assyrian Democratic Movement,paced nervously in his office as he watched the news from Qaraqosh.
In search of help, he called the United Nations mission to Iraq, the U.S. Embassy and the Iraqi military. He reached no one of influence, so he left messages.
"We're trying to stop those bloody guys," Mr. Kanna said, referring to ISIS. "I'm not confident we can. They are aggressive and have heavy weapons. We only have a few Kalashnikovs."
While he waited impatiently for his calls to be returned, Mr. Kanna recalled the days when Iraq's Sunnis, Shiites and Christians celebrated religious holidays together and intermarried, and Baghdad boasted a vibrant Jewish community.
In today's Iraq, Shiites make up about 60% of the population and Sunnis 32%, while Christians and other minorities compose 3%, according to the CIA World Factbook.
For Mr. Kanna, the intolerance of ISIS militants toward non-Sunni religious faiths isn't entirely to blame for the dwindling Christian community. Christians themselves, he said, have chosen to emigrate rather than struggle to keep their foothold in Iraq. He accuses Western nations,even the U.S. president,of encouraging their flight.
"I told Obama to stop the immigration of Christians. Stop this policy of vacuuming up the Christians of the Middle East. It is destroying the community," said Mr. Kanna, citing a letter he wrote to the White House several months ago.
His homily was interrupted by the ringing of his phone. It was a U.S. Embassy official returning his call.
"Hello. I just wanted to inform you that the biggest Christian community, Qaraqosh, is being attacked," Mr. Kanna said politely.
The embassy official asked Mr. Kanna to identify himself. He sighed.
"You met me yesterday."
— Laith al-Haydair contributed to this article.