SUDAN was bombing South Sudan again last week, only a couple of months after the two countries split apart. Sudan is mostly Muslim, and South Sudan is predominantly Christian, but the quarrel is about oil, not religion. And yet, it is really about religion too, since the two countries would never have split apart along the current border if not for the religious divide.

The Ivory Coast was split along the same Muslim-Christian lines for nine years, although the shooting ended last year and there is an attempt under way to sew the country back together under an elected government. But in Nigeria, Africa’s biggest country by far, the situation is going from bad to worse, with the Islamist terrorists of Boko Haram murdering people all over the country in the name of imposing sharia law on the entire nation.

“The situation we have in our hands is even worse than the civil war that we fought (in 1967-70, which killed between one and three million people),” said President Goodluck Jonathan. That’s a major exaggeration.

In an interview with Reuters, President Jonathan said: “If (Boko Haram) clearly identify themselves now and say...this is the reason why we are confronting government or this is the reason why we destroyed some innocent people and their properties, why not (talk to them)?” But it’s pointless: he already knows who they are and what they want.

“Boko Haram”, loosely translated, means “Western education is forbidden,” and the organisation’s declared aim is to overthrow the government and impose Islamic law on all of Nigeria. In a 40-minute audio message posted on YouTube two weeks ago, the group’s leader, Abubakar Shekau, threatened that his next step would be to carry out a bombing campaign against Nigeria’s secondary schools and universities.

This is not only vicious; it is also completely loony. There is no way that Boko Haram could conquer the entire country. Only half of Nigerians are Muslims, and they are much poorer than the country’s 80 million Christians. The Christian south is where the oil is, and the ports, and most of the industry, so that’s where most of the money is too. The same pattern is repeated in many other African countries: poor Muslim north; prosperous Christian south.

There was no plan behind this. Islam spread slowly to south from North Africa, which was conquered by Arab armies in the 7th century, while Christianity spread rapidly inland once European colonies appeared on the African coast in the last few hundred years. The line where Islam and Christianity meet runs across Africa about 1,100 km, north of the equator (except in Ethiopia, where the Christians have the highlands and the Muslims the lowlands).

In general, the Muslims ended up with the desert and semi-desert regions of Africa because Islam had to make it all the way across the Sahara, while the more fertile and richer regions nearer to the equator and all the way down to South Africa are mainly Christian because the Europeans arrived by sea with much greater economic and military power.

There probably won’t be a full-scale civil war in Nigeria this time around, but Boko Haram is targeting Christians indiscriminately. The Nigerian army, not best known for its discipline and restraint, is almost as indiscriminate in targeting devout but innocent Muslims in the northern states.

It will get worse in Nigeria, and it is getting bad again in what used to be Sudan, and Ethiopia is an accident just waiting to happen. Even Ivory Coast may not really be out of the woods yet. There is a small but real risk that these conflicts could some day coalesce into a general Muslim-Christian confrontation that would kill millions and convulse all of Africa.

Christianity and Islam have been at war most of the time since Muslim armies conquered half of the then-Christian world, from Syria to Spain, in the 7th and 8th centuries. There was the great Christian counter-attack of the Crusades in the 12th century, the Muslim conquest of Turkey and the Balkans in the 15th and 16th centuries, and the European conquest of almost the entire Muslim world in the 18th-20th centuries.

It is a miserable history, and in some places it is likely to continue for some time to come.