From Steve Bloomfield in Nairobi

AS the Islamic Courts fled the town of Jowhar, 50 miles northwest of Mogadishu, late last week, the DJs on Radio Jowhar did something they had not been able to do for six months: they played Western pop. For Jowhar residents it was confirmation that the Courts, who had introduced sharia law, banned music, films and football matches, had been defeated. Young men openly chewed qat, the mild stimulant the Courts had also banned.

Somali government troops, backed by at least 4000 Ethiopian soldiers, overran the Union of Islamic Courts (UIC), which had controlled large swathes of central and southern Somalia, including the capital, Mogadishu. Just four days after Ethiopia's prime minister, Meles Zenawi, announced that Ethiopian troops were inside Somalia, those soldiers were entering Mogadishu. The Courts fled to Kismaayo, a port town in the southeast and their final stronghold.

But the UIC's defeat has also brought chaos. Mogadishu, once known as the world's most dangerous city, may soon be seeking to reclaim its title. Checkpoints have returned, as have the souped-up 4x4s armed with rocket-propelled grenade launchers known as "technicals". Rival clan warlords, who once fought for control of every single street in the capital, are now doing the same all over again.

But asked to choose between pop and security, most Somalis would plump for the latter. The Islamic Courts, dismissed by the US as "terrorists", brought a semblance of law and order to towns that have known no such thing in the 15 years Somalia has been without a central government. Checkpoints and technicals became a rare sight in Mogadishu. Residents reported that they felt safe walking around the capital, something that had not been true when the city was run by rival warlords.

Mogadishu now appears to be back in the hands of the same warlords. Mohamed Jama Furuh, a former warlord and current member of parliament, reclaimed control of the capital's seaport. Others have reclaimed the airport and the old presidential palace.

The military defeat for the UIC has been remarkably swift. Just two weeks ago the Courts felt sufficiently confident of their military strength to plan an attack on Baidoa, the small town 130 miles west of Mogadishu that the weak transitional government was based in. But the military defeat has also become a political loss. Much of the UIC's support came from the influential Hawiye clan in Mogadishu. The Hawiye withdrew that support as the Somali government marched on Mogadishu, forcing the Courts to hand over weapons and vehicles the clan had provided.

Ethiopia's superior military strength has been the key factor. With 100,000 soldiers and training programmes from the US, they are the strongest military power in East Africa. A predominantly Christian country, Ethiopia feared the rise of a militant Islamic state on its doorstep. They found an ally in the US, which saw the Courts through the prism of the global war on terror.

Jendayi Frazer, US assistant secretary of state for African affairs, earlier this month asserted that the Courts were "controlled by al-Qaeda cell individuals". She claimed: "The top layer of the court are extremists. They are terrorists."

Few analysts dispute that the UIC had a hardline element that included some with links to known al-Qaeda operatives, but the idea that the entire organisation was run by terrorists appeared to be shared only by a handful of neoconservatives in Washington. It was certainly not believed by any Western diplomats, Americans included, based in the region.

But with America's tacit approval, Ethiopia was prepared to send troops to Somalia to bolster the weak, UN-backed government. The increasingly fragile government had little authority or popularity outside of Baidoa and their reliance on Ethiopia only deepened the resentment felt towards them by ordinary Somalis. Ethiopia and Somalia have fought two bitter wars in the past 45 years and the enmity felt by Somalis towards their neighbours runs deep.

But the planned attack on Baidoa by the UIC was all the encouragement Ethiopia needed. Claiming Somalia's legitimate government was under attack, Ethiopia's prime minister, Zenawi, announced the region's worst-kept secret: Ethiopian troops were indeed inside Somalia, despite his own repeated denials over the previous five months.

But with the UIC regrouping in Kismaayo, this may not be the end. The Courts' hardliners, known as the Shebab, have already threatened to carry out attacks in Ethiopia's capital, Addis Ababa. Kenya's capital, Nairobi, may also be a target. Ethiopian and Somali government troops are now heading towards Kismaayo with the aim of finishing the job.

However, success will not come with a military victory. The test Somalia's government faces now is a political one. In a country effectively controlled by dozens of separate clan factions, all prepared to fight for what they want, forming an effective national government is not going to be easy.