Forces from African Union countries have also performed in an "extraordinary" manner, Army Gen. Carter F. Ham told Soldiers Radio and Television during closing ceremonies for Southern Accord, a joint military exercise.
"They really have degraded the capability of al-Shabaab, an al-Qaida affiliate operating in Somalia, where most of Somali territory is no longer receptive to al-Shabaab," he said.
He said U.S. assistance has helped increase African countries' counter-terrorism capability.
While Somalia is becoming more stable, there are other trouble spots in Africa, Ham said. He cited Mali, saying about two-thirds of the country is controlled by terrorist groups.
Notable deaths of 2014 [PHOTOS]