As Christmas neared, an 85-foot-high tree presided over the little square in front of the Greek Orthodox Church of the Annunciation in Nazareth. Kindergarten children with Santa Claus hats entered the church and listened to their teacher explain in Arabic the Greek inscriptions on the walls, while a group of Russian pilgrims knelt on their knees and whispered in prayer. In Nazareth's old city, merchants sold the usual array of Christmas wares.

This year, however, the familiar rhythms of Christmas season in the Holy Land have been disturbed by a new development: the rise of an independent voice for Israel's Christian community, which is increasingly trying to assert its separate identity. For decades, Arab Christians were considered part of Israel's sizable Palestinian minority, which comprises both Muslims and Christians and makes up about a fifth of the country's citizens, according to the Israeli government.

But now, an informal grass-roots movement, prompted in part by the persecution of Christians elsewhere in the region since the Arab Spring, wants to cooperate more closely with Israeli Jewish society—which could mean a historic change in attitude toward the Jewish state. "Israel is my country, and I want to defend it," says Henry Zaher, an 18-year-old Christian from the village of Reineh who was visiting Nazareth. "The Jewish state is good for us."

The Christian share of Israel's population has decreased over the years—from 2.5% in 1950 to 1.6% today, according to Israel's Central Bureau of Statistics—because of migration and a low birthrate. Of Israel's 8 million citizens, about 130,000 are Arabic-speaking Christians (mostly Greek Catholic and Greek Orthodox), and 1.3 million are Arab Muslims.

In some ways, Christians in Israel more closely resemble their Jewish neighbors than their Muslim ones, says Amnon Ramon, a lecturer at the Hebrew University of Jerusalem and a specialist on Christians in Israel at the Jerusalem Institute for Israel Studies. In a recent book, he reports that Israeli Christians' median age is 30, compared with 31 for Israeli Jews and only 19 for Israeli Muslims. Israeli Christian women marry later than Israeli Muslims, have significantly fewer children and participate more in the workforce. Unemployment is lower among Israeli Christians than among Muslims, and life expectancy is higher. Perhaps most strikingly, Israeli Christians actually surpass Israeli Jews in educational achievement.

As a minority within a minority, Christians in Israel have historically been in a bind. Fear of being considered traitors often drove them to proclaim their full support for the Palestinian cause. Muslim Israeli leaders say that all Palestinians are siblings and deny any Christian-Muslim rift. But in mixed Muslim-Christian cities such as Nazareth, many Christians say they feel outnumbered and insecure.

"There is a lot of fear among Christians from Muslim reprisals," says Dr. Ramon. "In the presence of a Muslim student in one of my classes, a Christian student will never say the same things he would say were the Muslim student not there."

"Many Christians think like me, but they keep silent," says the Rev. Gabriel Naddaf, who backs greater Christian integration into the Jewish state. "They are simply too afraid." In his home in Nazareth, overlooking the fertile hills of the Galilee, the 40-year-old former spokesman of the Greek Orthodox Patriarchate in Jerusalem is tall and charismatic, dressed in a spotless black cassock. "Israel is my country," he says. "We enjoy the Israeli democracy and have to respect it and fight for it."

That is the idea behind the new Forum for Drafting the Christian Community, which aims to increase the number of Christians joining the Israel Defense Forces. It is an extremely delicate issue: Israeli Arabs are generally exempt from military duty, because the state doesn't expect them to fight their brethren among the Palestinians or in neighboring Arab countries. Israeli Palestinians, who usually don't want to enlist, say they often face discrimination in employment and other areas because they don't serve.

"We were dragged into a conflict that wasn't ours," says Father Naddaf. "Israel takes care of us, and if not Israel, who will defend us? We love this country, and we see the army as a first step in becoming more integrated with the state."

According to Shadi Khaloul, a forum spokesperson, the total number of Christians serving in the Israeli military has more than quadrupled since 2012, from 35 to nearly 150. This may seem a drop in the ocean, but it was enough to enrage many Palestinian Israelis. Father Naddaf says that his car's tires were punctured and that he received death threats, worrying him enough that he got bodyguards. Hanin Zoabi, an Arab-Muslim member of the Israeli parliament, wrote Father Naddaf a public letter calling him a collaborator and accusing him of putting young Christians "in danger." "Arab Palestinians, regardless of their religion, should not join the Israeli army," Ms. Zoabi told me. "We are a national group, not a religious one. Any attempt to enlist Christians is part of a strategy of divide-and-rule."

Many Arab Christians don't see it that way. "We are not mercenaries," says Mr. Khaloul, who served as a captain in an IDF paratrooper brigade. "We want to defend this country together with the Jews. We see what is happening these days to Christians around us—in Iraq, Syria and Egypt."

Since the Arab revolutions began in Tunisia in 2011, many Christians in the region have felt isolated and jittery. Coptic churches have been attacked in Egypt, and at least 26 Iraqis leaving a Catholic church in Baghdad on Christmas Day were killed by a car bomb. Islamists continue to threaten to enforce Shariah law wherever they gain control.

The Christian awakening in Israel goes beyond joining the IDF. Some Israeli Christian leaders now demand that their history and heritage be taught in state schools. "Children in Arab schools in Israel learn only Arab-Muslim history," says a report prepared by Mr. Khaloul and submitted to Israel's Ministry of Education, "and this causes the obliteration of Christian identity."

Some Israeli Christians even recently established a new political party, headed by Bishara Shlayan, a stocky, blue-eyed former captain in the Israeli navy who told me that he once beat up an Irish sailor in Londonderry who called him an "[expletive] Jew." The new party is puckishly called B'nai Brith ("Children of the Covenant"), and Shlayan says it will have Jewish as well as Christian members. Nazareth's mayor, Ramez Jaraisy, recently told the Times of Israel that Shlayan was a "collaborator" with the Israeli authorities.

"The current Arab political establishment only brought us hate and rifts," says Mr. Shlayan. "The Arab-Muslim parties didn't take care of us. We are not brothers with the Muslims; brothers take care of each other." Mr. Shlayan, who advocates better education, housing and employment for Israeli Christians, says he also dreams of turning Nazareth into an even busier tourist spot by erecting the world's biggest statue of Jesus.

Should this Christian awakening succeed, it would be yet another notable shift in the balance of power among religious groups in the Middle East.

—Mr. Schwartz is a former staff writer and senior editor for the Israeli newspaper Haaretz.