Sometimes Donald Trump gets it right. In February he cut off US military aid to the central African country of Cameroon because of its appalling human rights record (and didn't even offer to restore it if the Cameroon government dug up dirt on his political opponents at home). Last Friday he acted again, dropping Cameroon from a pact that promotes trade between sub-Saharan African countries and the US.
Okay, it probably wasn't really Mr Trump's idea. There's still a few professionals left in the State Department, and it was probably one of them who pushed it through. The appeal to Mr Trump may just be that he is punishing a country that is expanding its trade with China -- but the human rights abuses in Cameroon really are off the scale.
Cameroon's main claim to fame until recently was its ruler, Paul Biya, the oldest and longest-ruling dictator in the world (86 years old and in power for the past 42 years). But Mr Biya wasn't all that bad, apart from the usual corruption and the occasional political murder, until the downtrodden English-speakers started protesting seriously about two years ago.
The "anglophones", as they are known in majority French-speaking Cameroon, have been pushed into a corner basically because they don't fit the mould. A century ago hardly anybody in the region spoke either English or French, but the vagaries of colonial policy put some of the locals into the British empire and some into the French -- and then independence brought some of them back together again.
More than four-fifths of the 25 million Cameroonians live in French-speaking parts of the country. Only one-fifth live in the anglophone region -- but that region is right up against the border with Nigeria, where around 190 million people use English as their lingua franca.
That shouldn't have been a problem if Cameroon had respected the rights of its English-speakers, but having giant Nigeria right next-door made the country's francophone ruling elite uneasy. Predictably, but very stupidly, Mr Biya and his cronies saw separate institutions for the anglophones as a potential cause for division, and started eliminating them.
They unilaterally changed the country's federal structure into a unitary one, ending anglo self-government. They replaced English-speaking judges and English common law with francophone judges and French law. Government jobs automatically went to "loyal" francophones even in anglophone areas.
Every step they took to erase the differences between anglos and francos only deepened the divisions between them. Finally the anglophones began publicly protesting -- and when their representatives were all jailed, more radical protesters began demanding independence for the anglophone region, which they dubbed "Ambazonia". They got arrested too, and the next wave of protesters turned to violence.
It wasn't very effective violence at first, because they lacked weapons, experience and organisation, but you can always buy the weapons in Nigeria or take them from dead regime soldiers and police. For the rest, you just climb the learning curve -- and by now, two years in, it's a full-scale insurgency, so both sides are behaving with extreme stupidity.
The regime should be making the kind of concessions that would reconcile its anglophones to being Cameroonian citizens, but it's doing nothing of the sort. The thugs have taken over, and its soldiers and police are acting as unpaid recruiters for the rebels, killing young anglo men at random and burning whole villages where some local resident is suspected of being one of the "Amba-boys".
The rebels are equally devoted to self-harm. They have closed down all 6,000 schools in the anglophone region because the national curriculum requires the students to be taught French. Not taught in French; just taught to speak French. If the teachers try to keep the schools open, the rebels burn them down. Sometimes they kill the teachers too.
The original blame for the breakdown rests almost entirely with the Biya regime, but the rebels are catching up fast in the stupidity stakes. It has become a classic guerilla war, in the worst sense of the word, and it could blight the lives of an entire generation.
What makes it even more bizarre is that it's not even about genuine ethnic, religious or linguistic differences. Cameroon has enough of those: many different tribes, Muslims in the north and Christians in the south, and around 250 different languages, some spoken by only a few thousand people. But this war is about which foreign language people speak!
It is a mercifully rare problem in Africa, because while most African states contain many languages, they have kept the borders that the colonialists imposed. Everybody living inside those borders has therefore inherited the same colonial language, usually French, English or Portuguese, and uses it to communicate with their fellow-citizens whose home language is different.
It's an arbitrary solution with its roots in tyrannical oppression by foreigners, but there's no other way that large numbers of Africans could share a modern state together. Most of the linguistic groups are too small. And Cameroon shows what is all too likely to happen, human beings being what they are, if that situation does not prevail.