Various factions began competing for influence in the power vacuum that followed, which precipitated an aborted UN peacekeeping attempt in the mid-1990s. A period of decentralization ensued, characterized by a return to customary and religious law in many areas as well as the establishment of autonomous regional governments in the northern part of the country. The early 2000s saw the creation of fledgling interim federal administrations, culminating in the establishment of the Transitional Federal Government (TFG) in 2004. In 2006, the TFG, assisted by Ethiopian troops, assumed control of most of the nation's southern conflict zones from the newly formed Islamic Courts Union (ICU). The ICU subsequently splintered into more radical groups, notably Al-Shabaab, which have since been fighting the Somali government and its AMISOM allies for control of the region. In 2011, a coordinated military operation between the Somali military and multinational forces began, which is believed to represent one of the final stages in the war's Islamist insurgency.