As Hatem al-Far waited with dwindling hope for an Israeli permit that would allow him out of Gaza this Christmas, he showed a picture on his phone of his first grandson, eight-month-old Ibrahim, and wondered when, if ever, he would see him in the flesh.

This year Far, 53, has a double reason for wanting permission to leave Gaza: he wants to attend the Greek Orthodox midnight mass in Bethlehem’s Church of the Nativity with his family and attend Ibrahim’s christening, which has been postponed in the hope that his grandfather will make it to the West Bank. “I’m not asking for much,” he said. “I’m living in one Palestinian city, and all I want is to travel to another Palestinian city for a few days.”

Compared with the privations suffered by much of Gaza, the problem faced by Far may not sound overly harsh. But the separation threatening the family is symbolic of the plight of Gaza’s Christians, a community smaller, and arguably under greater pressure, than at any time in its history of at least 1,800 years.

If he is allowed out to join his wife – who has a Christmas permit and has already left for the West Bank – Far will certainly return to his native Gaza, which, like most Palestinian Christians here, he has no desire to leave for good. He works for the Catholic NGO Caritas, coordinating its mobile clinics in Gaza, including one set up recently to treat those shot by Israeli troops while taking part in border protests against the Gaza blockade, which has cost the lives of 220 Palestinians since March.

But three years ago his daughter Sally, 22, used her Christmas exit permit to marry a man from the West Bank and settle in Jenin, where Ibrahim and his older sister were born. Having been granted a Christmas exit permit last year, one of Far’s sons, Randy, 20, also left Gaza and is now living in Ramallah, where he works in a restaurant.

Far acknowledged that his youngest son Ramzi, 17, may use the Christmas permit he has been granted to follow his brother. Already an expert player of the qanun, a musical instrument he has studied at Gaza’s Edward Said Conservatory, Ramzi is keen to advance his training.

Another son, Rami, 25, is a business graduate with a place on a Christian community job-creation scheme, but with no prospect of a job after that would probably like to do the same if he had a permit, which like his father, he has not – so far – received this year. “You know Gaza,” said Far. “There are no opportunities; the economy, safety and security, these are the things young people here worry about.” For Far, it presents a painful dilemma. “I don’t want my four children to be away from me. I want my sons around me. I can’t decide what to tell them. If I say go and it doesn’t work out, then it’s bad. But if I say stay and they have nothing, it’s also bad.”

Far’s remaining sons are not alone in contemplating emigration. A recent poll by the respected Palestinian Centre for Policy and Survey Research found that 50% of the two million Palestinians in Gaza want to emigrate (as opposed to 22% from the West Bank), lacking only the chance to do so.

It is hardly surprising after a mainly Israeli but also Egyptian 11-year blockade that has left Gaza’s economy in what the World Bank describes as “freefall”, with unemployment at 53% – and more than 70% among the under-25s. Over the same period three Israeli military onslaughts against Hamas have killed more than 2,000 non-combatant Palestinians, according to the Israeli human rights agency B’Tselem.

“We are Palestinians first and last,” said Christian activist George Anton. “We are totally suffering from the occupation.”

Last month Gaza went to the brink of a fourth war when a botched Israeli intelligence operation was exposed near Khan Yunis, triggering a firefight that left an Israeli colonel and seven Palestinian militants, including a Hamas commander, dead. Hamas fired more than 300 rockets into Israel, while Israeli forces launched their fiercest bombardment of the Strip since 2014.

Although the Israeli prime minister, Benjamin Netanyahu, swiftly de-escalated the crisis by agreeing to an Egyptian-brokered deal, there is little sign as yet of a more formal ceasefire in return for significant steps to end the blockade.

In one sense the Fars’ story is untypical. The large majority of Christians who travel to the holy sites in Jerusalem and Bethlehem return home each year. But the small minority who don’t are part of a much longer story, the shrinking of Gaza’s Christian community over many centuries.

Today’s Greek Orthodox church in the Zeitoun district of Gaza City stands on the site from which its fourth-century patron saint began converting local inhabitants from paganism. By the sixth century most Gazans were Christian, following a long era, economically and culturally rich, under the Roman empire. In 570 an Italian pilgrim wrote: “Gaza is a lovely and renowned city, with most noble people distinguished by every kind of liberal accomplishment. They are welcoming to strangers.” (Palestinians in Gaza still are).

But although Gazans switched rapidly to Islam after Arab victories in the seventh century, Christianity did not die out. There is archaeological evidence that what rapidly became a minority religion coexisted peacefully with the new Muslim one – as it still does today. But its shrinking has accelerated during the military turbulence of the past half-century.

In the mid-1960s, before the six-day war and Gaza’s occupation by Israel, there were about 6,000 Christians in Gaza; today there are an estimated 1,100. Samir Tarazi, 60, a member of one of Gaza’s largest Christian extended families, said: “Sometimes you wonder for how long there will still be a community here.”

For now, however, it is very much alive. True, there hasn’t been a municipal Christmas tree in Gaza City’s Square of the Unknown Soldier since the beginning of the second intifada in 2000. But they are lit up in every Christian home, even the poorer ones.

On Saturday night an elaborately decorated four-metre steel “tree” was unveiled at a celebration for 400 people at the YMCA, which has been at the heart of Gaza’s Christian community since 1954.

In the city’s Sheikh Radwan neighbourhood, the Gift Palace shop was packed with Chinese-made plastic trees, baubles, Santa hats, and even racy above-the-knee “Father Christmas” nightdresses, all of which appealed, said owner Abdulla Abdel Majd, to Muslims as well as Christians. Majd admitted “a few Sheikhs” had complained about the display, but he was doing a brisk trade, although down on last year.

And Christian parents were busy preparing “Barbara”, the squishy cakes of nuts, cinnamon and aniseed that Arab Christians share with family, friends and neighbours between St Barbara’s Day on 4 December and Christmas – which, for the Orthodox, the large majority of Gaza’s Christians, is on 7 January.

But religion is at the heart of the celebrations. Last Sunday’s sung mass at the Latin (Catholic) church incorporated the Christmas liturgy in honour of the Italian celebrant, Archbishop Pierbattista Pizzaballa, making his seasonal visit from Jerusalem. While acknowledging it might be a strange time to talk of “joy, hope and peace”, the archbishop told worshippers: “God is not just in heaven but among us. Our faith creates something that goes beyond human possibilities.”

He had a point. The churches’ three private schools, whose fees range from $700-$900 a year, serve mostly Muslim pupils, and the Catholic Rosary Sisters provide the sole care for some of the most severely disabled children from across the Strip. A vocational centre run by a Christian Gazan, Iman Jelda, for the Near East Council of Churches serves 140 boys and young men aged 14 to 23, mainly from poor backgrounds, and all Muslims. In the cooling and air-conditioning department – where one trainee, Mohammed Satari, has a degree in accounting but thought he had a “better chance of a job here” – Jelda asked the group how many would like to leave Gaza. All put their hands up.

The NECC vocational centre exemplifies the high level of integration Christians enjoy – for the most part – with the wider and overwhelmingly Sunni Muslim community. Not that their relations have always been trouble-free. In 2006, when the Danish publication of cartoons depicting Muhammad sparked outrage, the Latin church received a series of threatening – and unsigned – faxes. In October 2007, the Baptist manager of a Christian bookshop was murdered, apparently by Salafist extremists.

After both incidents Hamas pledged to give its protection, and Bassem Naim, an international relations spokesman for the faction, insisted last week: “We are one family. The Christians are part of our society.” Senior Christians insist the relations with Hamas are ones of mutual respect.

Christian women who dress less conservatively than many (although by means all) of their Muslim counterparts and never cover their hair, can be subject to limitations. Hijabs are compulsory, for example, at the Islamic University of Gaza (although not at Al-Azhar, which is favoured by many Christian students).

Nor, acknowledged Anton, would government ministries “here in Gaza ever hire a lady with uncovered hair … This is our community and this is how the people think. We cannot ignore this.”

Dana Tarazi, 25, admitted that, while she drew no complaints in the city centre, she usually got a private taxi to work rather than share with other passengers on a route that passes through more conservative areas.

But like some other Christian young women she said that the atmosphere had become more liberal in the past few years. And the majority of friends at her secret Santa party this week would be Muslim.

But permits to leave for Bethlehem and Jerusalem at Christmas remain a problem, partly because they divide families. Tarazi, who feared last week that her father, Daoud, would be the only member of her family to secure one, said: “Sometimes there are families where only the children get the permits, so they cannot go.”

The Israeli military said it had granted 401 permits to adults and 219 to children under 16. But, perhaps ominously for Far, it warned that if those leaving did not return to Gaza it would “influence” the allocation of permits to their close family members.

Archbishop Pizzaballa, when asked about the permits, said: “We shouldn’t have to ask for permission at all. It should be our right. The international community should be doing everything it can to change the humanitarian situation here, including the right of citizens to move.”

Although data is hard to come by, many Christians tend to be among the less economically stricken of the broad mass of Gaza’s population, as well as having family and community networks which can welcome them abroad or in the West Bank if they leave.

However, there are also poorer ones. Wadir Turk, 52, who is unemployed, and his Egyptian wife Intisar, 45, could hardly afford a Christmas tree this year for their three children on the 1,000 shekels (£210) a month Intisar earns at the Rosary Sisters’ disabled centre and meagre social security payments they receive from the Palestinian Authority.

Nevertheless, a 2014 YMCA-sponsored survey estimated that 41% of Christians are graduates, compared with 13.4% of the whole Gazan population, and illiteracy is at 1.1% compared with an overall 3.6%. It also recorded that unemployment among recent Christian graduates was about 60% and would be higher without community-based job-creation and training schemes.

This has not stopped young Palestinian Christians having a positive outlook. Vivian Ayad, 22, insisted that, as long as her Muslim Palestinian friends could not travel in and out of Gaza, they would want to leave – but predicts that after 20 years or so they will ache to come back.

While admitting she was “very worried” about the shrinking of Gaza’s Christian community, Ayad – recently married and now completing a five-year pharmacy course at Al-Azhar university – was determined to stay and find a job as a qualified pharmacist. It is a highly responsible job, because many drugs prescribed elsewhere are sold over the counter, especially for poorer customers who cannot afford doctors’ fees. “But I’m a little bit optimistic. I think I can do it,” she said.

Dana Tarazi’s mother, Suzan, actually encouraged her two sons and elder daughter to leave – in their cases through Egypt. But she was clear that, if there was a just peace, an end to the Israeli blockade and a future for Gaza, “I will beg them to come back”.