Across the Middle East, Christian communities today find themselves the victims of widening repression: massacres, expulsions, and brutally enforced restrictions on the right to worship have all become commonplace. Such persecution has now reached the point where, in the region that was once its birthplace, Christianity’s very existence is under threat.

Radical armed groups such as al-Qaeda and the Islamic State of Iraq and Sham (ISIS) justify their offensive against the “infidels” with reference to new interpretations of jihad, the Islamic tradition of holy war, that have burgeoned in the region since the US-led invasions of Afghanistan and Iraq at the beginning of the century.

The impact on Christian communities is visible for all to see. In Iraq, the Christian population has withered from well over one million to just 300,000. In Syria, where the word “Christian” was first coined more than two millennia ago, at least half a million Christians, one third of the total, have fled their homes. In Egypt, where the Coptic Church, with its seven million adherents, is as old as the Church of Rome, Christians are emigrating in waves after being squeezed between those who blame them for the 2013 ousting of the Muslim Brotherhood government and a new military dictatorship that is heedless of their civil rights.

In this compact, fast-paced survey, Dan Williams pulls together extensive, first-hand reportage, salient historical antecedents, and intelligent political analysis to trace the contours of an unfolding tragedy. The situation of the Christian communities, he notes, has always been a barometer of turbulence in the Middle East. On this reading, storms clouds are today gathering fast.