The current conflict in Somalia is an outgrowth of the 2006–09 war, which was fought largely between Islamist militia groups and the armed forces of Ethiopia and Somalia’s Transitional Federal Government. The Islamic Courts’ Union (ICU) was a prominent Islamist militia, which gained control over much of southern Somalia during 2006 but was defeated by government and Ethiopian troops by the end of the same year. Hardline elements from the ICU splintered to form the militant groups al-Shabaab and Hizbul Islam, which merged in 2010 and joined al-Qaeda in 2012. Responding to al-Shabaab, forces from Kenya, Ethiopia, Djibouti, Burundi, Uganda and Sierra Leone, among others, have joined the African Union Mission in Somalia (AMISOM) to fight the rebels. The combined forces, along with the troops of Somalia’s first formal government in 21 years and pro-government militias such as Ras Kamboni, have made significant territorial advances against al-Shabaab, which has conserved its fighting strength through tactical withdrawals. The Islamist militant group has begun a reversion to guerrilla tactics in Somalia and Kenya in response to its losses.