With a small military training program, the United States military has joined efforts to fight a brutal insurgency that has devastated northern Mozambique. American Special Forces soldiers began training Mozambican troops this week as part of an effort to repel a spreading insurgency in northeastern Mozambique that American officials say is linked to the Islamic State. The insurgency, near some of the world’s biggest gas reserves, has killed at least 2,000 civilians and displaced another 670,000. The American program is modest in size and scope: a dozen Army Green Berets are to train Mozambican marines for the next two months....