Pope Francis’s visit to the United Arab Emirates this week will be greeted enthusiastically. Some 120,000 people are expected to turn out for his mass in a sports stadium in Abu Dhabi – as many as turned out in Dublin when he travelled to historically Catholic Ireland last year. The first visit by a pontiff to the Arabian peninsula, the birthplace of Islam, highlights the complications of the religious situation in the Middle East, and more widely the issues of Christian-Muslim relations.

There may be as many as 2 million Christians in the Middle East today. Despite nearly 16 years of war and sometimes brutal persecution in the aftermath of the invasion of Iraq, many remain in the lands that were the cradle of Christianity. In part this is because it is still made as hard as possible for them to leave the region. The Christians of Iraq have largely been driven from their homes by persecution, as have some of the Christians of Syria, where a number have taken the side of the Assad dictatorship. But they have ended up in refugee camps rather than reaching notionally Christian Europe.

At the same time as the long-established Christian populations of the north and west of this region have been under terrible pressure, to the south and west of the region the Gulf states, including Saudi Arabia, have imported hundreds of thousands of labourers and servants from south Asia and the Philippines and many of these people are Christian. They are more or less permitted to practise their religion, though never to make converts. There are legal Christian churches in all the Gulf states bar Saudi Arabia. It can be argued that Christians in some of those countries are much less persecuted than those in Pakistan, where Asia Bibi spent eight years on death row for blasphemy, and even after her acquittal had to be held in protective custody until flown to safety in Canada this week.

In the wider picture, the relations between Christians and Muslims may be one of the great faultlines of the century. Neither monotheism is monolithic. Pope Francis has a unique position in these tensions because he heads the largest organised religious grouping in the world: there are more Muslims than Catholics in the world but there is no Muslim leader with as much power over so many followers.

This is a not unmixed blessing. The existence of so much power is a constant temptation both to those who hold it and still more to those who want it. Pope Francis has tireless enemies. There are Christians in Africa, the US, and indeed Europe, who see Islam as an eternal and existential foe, mirroring the attitudes of their jihadi enemies; there is a strain of rightwing Christianity which defines European civilisation itself by its opposition to Islam. And because the Vatican is a transnational organisation, it must do business with some of the most unsavoury governments in the world.

Pope Francis has been accused of betraying the persecuted church in China by compromising with the government over the appointment of bishops. The UAE is an enthusiastic and essential force in the Saudi-led coalition’s campaign in Yemen, where the devastating war has left half the country on the brink of starvation. Pope Francis called for an end to the humanitarian crisis there before leaving the Vatican, but seems unlikely to raise the issue with his hosts, any more than he used the word Rohingya when he visited Myanmar last year. Even so, the demonstration that Christians can worship peacefully and in large numbers in a Muslim country will send an important, and welcome, signal round the world.