KARTMIN, TURKEY -- Christians have lived in these parts since the dawn of their faith. But they have had a rough couple of millennia, preyed on by Persian, Arab, Mongol, Kurdish and Turkish armies. Each group tramped through the rocky highlands that now comprise Turkey's southeastern border with Iraq and Syria.

The current menace is less bellicose but is deemed a threat nonetheless. A group of state land surveyors and Muslim villagers are intent on shrinking the boundaries of an ancient monastery by more than half. The monastery, called Mor Gabriel, is revered by the Syriac Orthodox Church.

Battling to hang on to the monastic lands, Bishop Timotheus Samuel Aktas is fortifying his defenses. He's hired two Turkish lawyers -- one Muslim, one Christian -- and mobilized support from foreign diplomats, clergy and politicians.

Also giving a helping hand, says the bishop, is Saint Gabriel, a predecessor as abbot who died in the seventh century: "We still have four of his fingers." Locked away for safekeeping, the sacred digits are treasured as relics from the past -- and a hex on enemies in the present.

The outcome of the land dispute is now in the hands of a Turkish court. Seated below a bust of Mustafa Kemal Ataturk, modern Turkey's secular founding father, a robed judge on Wednesday told the feuding parties that he would issue a ruling after he visits the disputed territory himself next month.

The trial comes at a critical stage in Turkey's 22-year drive to join the European Union. When it first came to power in 2002, the ruling AK party, led by observant Muslims, pushed to accelerate legal and other changes demanded by Europe for admittance into its largely Christian club. But much of the momentum has since slowed. France has made clear it doesn't want Turkey in the EU no matter what, while Turkey has seemed to have second thoughts.

A big obstacle is Turkey's continuing tensions with its ethnic minorities, notably the Kurds, who account for more than 15% of the population and are battling for greater autonomy. Also fraught, but more under the radar, is the situation confronting members of the Syriac Orthodox Church, one of the world's oldest and most beleaguered Christian communities. The group's fate is now seen as a test of Turkey's ability to accommodate groups at odds with "Turkishness," a legal concept of national identity that has at times been used to suppress minority groups.

The dispute over Mor Gabriel is being closely watched here and abroad. The EU and several embassies in Ankara sent observers to a court hearing in February, and a Swedish diplomat attended this week's session. Protection of minority rights is a condition for entry into the EU.

Founded in 397, Mor Gabriel is one of the world's oldest functioning monasteries. Viewed by Syriacs as a "second Jerusalem," it sits atop a hill overlooking now solidly Muslim lands. It has just three monks and 14 nuns. It also has 12,000 ancient corpses buried in a basement crypt.

The bishop's local flock numbers only 3,000. Mor Gabriel's influence, however, reaches far beyond its fortress-like walls, inspiring and binding a community of Christians scattered by persecution and emigration. There are hundreds of thousands more Syriac Christians across the frontier in Iraq and Syria and in Europe. They speak Aramaic, the language of Jesus Christ.

"The monastery is all we have left," says Attiya Tunc, who left for Holland as a child and returned this February to find her family's village near here reduced to ruins and overrun with sheep, since most of the villagers abandoned it. Ms. Tunc says she came in response to telephone call from Bishop Aktas appealing to former residents to come back and show their support in the land battle.

Historical Claims

Turkish officials say they have no desire to uproot Christianity. They point to new roads and other services provided to small settlements of Syriac Christians who have returned in recent years from abroad.

Mustafa Yilmaz, the state's senior administrator in the area, says Turkey wants to clarify blurred property boundaries as part of a national land survey, something long demanded by the EU. He says the monastery could lose around 100 acres of land currently enclosed within a high wall, meaning a loss of about 60% of its core property. Some of that could be reclassified as a state-owned forest, with the rest claimed by the Treasury on the grounds that it's not being used as intended for farming or other purposes.

Syriac Christians see a more sinister purpose. They say the Turkish state and Muslim villagers want to grab Christian land and force the non-Muslims to leave. "There is no place for Christians here" until Turkey changes in fundamental ways, says Ms. Tunc.

The dispute has spurred some Muslims in neighboring villages to launch complaints against the monastery. Mahmut Duz, a Muslim who lives near Mor Gabriel, lodged a protest last year to the state prosecutor in Midyat, a nearby town. Mr. Duz alleged that the bishop and his monks are "engaged in illegal religious and reactionary missionary activities."

Mr. Duz urged Turkish authorities to remember Mehmed the Conqueror, a 15th-century Ottoman ruler who routed Christian forces and conquered the city now called Istanbul for Islam. He said Turkish officials should recall a vow by the Conqueror to " 'cut off the head of anybody who cuts down even a branch from my forest.' " Bishops and priests, Mr. Duz told the prosecutor, can keep their heads, but "you must stop the occupation and plunder" of Muslim land by the monastery.

No one at the monastery has been prosecuted for the crimes alleged by Mr. Duz and other villagers. The monastery says these claims are ludicrous. It says it tutors 35 Syriac Christian school boys in Aramaic and religion but conducts no missionary activities.

Syriac Christians take an even longer view than Mr. Duz. They deride local Muslims as newcomers, saying Mor Gabriel was built two centuries before Islam was founded. "Mohammed did not exist. The Ottoman Empire did not exist. Turkey did not exist," says Issa Garis, the monastery's archdeacon.

A Long List of Raids

Syriac Christians have indeed been living -- and often suffering -- here for a very long time. Mor Gabriel's history is a "long list of raids, wars, droughts, famines, plagues and persecutions," says British scholar Andrew Palmer. "Time and again, they've had to start again from nothing."

In the eighth century, plague swept through the area and took the lives of many of Mor Gabriel's monks. Survivors dug up the body of Saint Gabriel, the monastery's seventh-century abbot, and propped him up in church to pray for help. The plague, according to tradition, passed.

When disease later ravaged a Christian center to the north, Saint Gabriel's right hand was cut off and sent there to help. One of the fingers was then removed and dispatched to avert another crisis elsewhere. The finger is now missing.

As Islam extended its reach, the monastery shut down repeatedly, but always reopened. It was attacked by Kurds, Turks and then Kurds again. In the 14th century, Mongol invaders seized the monastery and killed 40 monks and 400 other Christians hiding in a cave. Perhaps the biggest blow of all came in the modern era, when Turkey's slaughter of Christian Armenians during World War I led to massacres of Syriac Christians, too. The patriarch of the Syriac Orthodox Church later decamped to Syria.

Ms. Tunc, the woman now living in Holland, grew up with stories of massacred relatives. Her father "told us never to trust Turks or Kurds," and ordered her to master Dutch ways "because we could never go back."

Her family and many others left Turkey in the 1980s during a brutal conflict between Turkish soldiers and Kurdish guerrillas. Syriac Christians, viewed with suspicion by both sides, frequently got caught in the crossfire.

The exodus drained towns and villages of Christians, including Midyat, the town where the court is reviewing the land dispute. Midyat used to be almost entirely Christian but now has just 120 non-Muslim families out of a population of 60,000. The town has seven churches, but just one preacher.

Running a Tight Ship

As Christians fled, Bishop Aktas took charge of Mor Gabriel. He'd earlier studied in New York but found the U.S. too permissive. "I didn't like America. It is not for monks like me," he says.

By some accounts, he ran a very tight ship. Aydin Aslan, a student there from 1978 until 1983, says discipline was extremely strict, each day devoted to study and prayer. "It was like a prison," recalls Mr. Aslan, who emigrated to Belgium.

Alarmed by a spate of thefts and determined to keep Muslim neighbors from encroaching, Bishop Aktas started building a high wall around his land. When Muslims from the village of Kartmin planted crops and grazed livestock near a well on monastic property, monks and school boys filled the well with stones to keep them away.

Muslim resentment grew against the monastery, which was being bolstered thanks to funds from abroad. Following a drop-off in fighting between the Turkish military and Kurdish guerrillas after 2000, Syriac Christian ?migr?s seized on the relative calm. They poured money in to rebuild old churches, expand the monastery compound and build summer homes.

A few decided to move back for good. Jacob Demir returned from Switzerland with his family to a new villa on the outskirts of Midyat. "They thought we would go to Europe and melt away," says Mr. Demir. Instead, he says, exile only made him more aware and assertive of his Syriac identity. (His older children are less enthusiastic: A daughter stayed behind in Europe and a son who came back to Turkey left when he discovered how low local salaries are.)

The return to Turkey of relatively prosperous Christians helped the economy and provided jobs in construction. But it also needled some Muslims, especially when returnees began to claim abandoned property occupied by Muslims.

Turmoil in neighboring Iraq added to the unease. After the 2003 U.S. invasion, hundreds of thousands of Syriac Christians in Iraq fled mainly to Syria and Jordan as security collapsed and Muslims turned on their neighbors. Iraq's most prominent Syriac Christian, Saddam Hussein's foreign minister Tariq Aziz, was arrested by the U.S. Acquitted this week in the first of three cases against him, he remains in jail on other charges relating to the massacre of Iraqi Kurds in the 1980s.

As uncertainty mounted about the future of the Syriac church, officials in Midyat were ordered to survey all land in their area not yet officially registered. Surveyors, armed with old maps and aerial photographs, began fanning out through villages trying to work out who owned what.

Last summer, officials informed the monastery that big chunks of territory it considered its own were actually state-owned forest land. The monastery wall was declared illegal. Surveyors also redrew village borders, expanding the territory of three Muslim villages with which the monastery had long feuded.

The monastery went to court to challenge the decisions. Three village chiefs filed a complaint against the monastery with the Midyat prosecutor. Bishop Aktas, they complained, had destroyed "an atmosphere of peace and tolerance" and should be investigated.

The monastery's ?migr? lobby swung into action. Late last year and again in January, Syriac activists organized street demonstrations in Sweden and Germany. Yilmaz Kerimo, a Syriac Christian member of the Swedish parliament, protested to Turkey's Ministry of Interior, demanding an end to "unlawful acts and brutalities" at odds with Turkey's desire to join the EU.

Ismail Erkal, the village head here in Kartmin, one of the three settlements involved in the dispute, blames Bishop Aktas for stirring tempers. "This bishop is a difficult person," says Mr. Erkal. Standing on the roof of his mud-and-brick house. Looking out towards the monastery, he points to swathes of monastic land which he says should belong to Kartmin. His village used to have a church but, with no Christians left, it is now a stable. Next door is a new mosque.

Mr. Erkel says Islam "does not allow oppression," and denies any plan to get the last Christians in the area to leave.

Bishop Aktas says the message is clear: "They want to make us all go away."

Write to Andrew Higgins at andrew.higgins@wsj.com