Earlier this month, al-Shabab militants targeted a Somali army base near Mogadishu, killing at least five soldiers. It was the latest in a string of attacks going back to December 2014, when about 25 attackers disguised in Somali army uniforms penetrated the heavily fortified airport of Mogadishu, the main base for the African Union Mission in Somalia (AMISOM), wounding four.

The attacks highlight how, despite being pushed out of Somalia’s capital, Mogadishu, in 2011 and having suffered a steady loss of territorial control since, al-Shabab continues to be the main obstacle to Somalia’s political transition. It has also emerged as a major threat to security in neighboring Kenya. Why, after those setbacks, has al-Shabab’s capability to mount both conventional military operations and high-casualty terrorist attacks arguably increased? ...