The US base at Camp Lemonier in Djibouti is a key operational asset in a troubled region, with al-Qaeda active in nearby Somalia and Yemen. Some 3,000 US troops, as well as armour, fighters and drones are based there. But the US is also experimenting with a different kind of military mission- soft power through soldiers as aid workers, in an effort to deny militant extremists support among Africa's poor. The BBC World Service's Dan Damon has been given rare access to the US operation.
In a one-room library in the remote Djiboutian town of Ali Sabieh, Capt Courtney Sanders, a US soldier from Mississippi, is teaching children how to read English.
She and her team helped build the library and hold regular conversation classes there.
Capt Sanders' Civil Affairs team is part of a counterinsurgency mission with a difference.
Instead of sending in fighting troops once trouble has started in a poor country, the US is getting its soldiers to work on projects that, it is hoped, will build enough stability and opportunity to encourage the people of East Africa to hold onto peace and not fight over scarce resources.
"Since 9/11, the US government has gone through a profound shift in its philosophy behind how operations are conducted in the Horn of Africa," says Col William Hollingsworth, one of the longest serving members of the Combined Joint Task Force – Horn of Africa, or CJTF-HOA, which is coordinating the humanitarian side of soldiering here.
"The 'bumper sticker' name for this is the 3D process," he says.
Defence, diplomacy and development are the 3 Ds, designed as a virtuous triangle of American power projected overseas.
James Swan, ambassador to Djibouti, talks about the US military's work in the country
Air strikes
The base for the CJTF, Camp Lemonier in Djibouti City, houses plenty of conventional military firepower.
In a hanger on the airstrip, there is a Predator