The poster, designed by popular Somali cartoonist Amin Amir, is striking: it shows a militant, his face obscured by a scarf and a gun strapped to his back, feeding a baby – representing Somalia – with a grenade-shaped bottle. “Protect our children,” the tagline reads in Somali and English. Another shows a would-be suicide bomber with blood-drenched hands. “Stop the barbaric violence,” it says.

But it will take far more than a mere poster campaign to dislodge from Somalia the al-Shabaab militants that controlled Mogadishu and much of the country before they were driven from the capital by African Union troops and Somali forces two years ago.

The group still holds sway across southern Somalia and, as the deadly September attack on Nairobi’s Westgate mall demonstrated, the threat it poses continues to metastasise beyond the country’s borders.

Al-Shabaab (the name means “The Youth” in Arabic) is an al-Qaeda affiliated organisation that evolved from an Islamist movement that ruled Mogadishu until it was uprooted by Ethiopian forces that invaded Somalia in 2006. It contains two overlapping currents: nationalist-minded elements focused on ousting both the central government and the African Union force known as Amisom in order to create a fundamentalist Islamic state in Somalia; and foreign-backed radicals with more transnational goals.

In recent years, al-Shabaab has recruited from Somali diaspora communities in Europe and the US, particularly in Minnesota, home to America's largest Somali population. A prominent figure in al-Shabaab propaganda material was Alabama-born Omar Hammami (aka Abu Mansour Al-Amriki). Hammami, who featured in several al-Shabaab videos, is said to have fallen out with the group before reportedly being killed in a gun battle with his erstwhile associates in September.

In territories it controls, al-Shabaab enforces its own harsh version of sharia law, carrying out stonings and amputations to punish adulterers and thieves. “Al-Shabaab are like a disease that kills the people,” one man who fled an al-Shabaab enclave told me as famine ravaged Somalia’s southern flank in 2011. Others I met in the south that year insisted the group’s ideology was alien to interpretations of Islam more traditionally practised in Somalia. “Theirs is an imported version of Islam,” says Nicholas Kay, the UN’s special representative for Somalia. “They are like cuckoos in the nest.”

While al-Shabaab’s activities have mainly focused on targets within Somalia – with assassinations, suicide bombings, roadside bombs and the use of grenades common tactics – it has also proven capable of carrying out sophisticated attacks – like the Westgate siege – elsewhere in east Africa.

'No borders'
"Al-Shabaab is based on the ideology of al-Qaeda and this ideology has no citizenship. They are transcontinental, they are global," says Somalia's president Hassan Sheikh Mohamud. "The al-Shabaab phenomenon has no borders as we have seen recently with the Nairobi attack. The Somali people want to see al-Shabaab defeated but this is an international war and we need support."

The Westgate atrocity was not the first time the group had struck outside Somalia: in 2010, it carried out coordinated suicide bombings that killed 74 people who had gathered to watch the World Cup in the Ugandan capital, Kampala. Uganda has contributed more than 6,000 personnel to Amisom, making it the largest contingent in the UN-backed force. Other participating nations include Kenya, Burundi, Djibouti and Sierra Leone.

“We are sending a message to every country that is willing to send troops to Somalia that they will face attacks on their territory,” said a spokesman at the time.

Security has been stepped up in Kampala following the recent Nairobi attack. "We are concerned but it will not intimidate us because we must clean our region of these fanatical fellows," Uganda's president Yoweri Museveni told me. "There is no shortcut."

Both Museveni and Mohamud insisted that the Westgate siege was a sign that al-Shabaab has been weakened as a result of both Amisom’s push against it and recent internal power struggles.

“When you go for a soft target like people who are having coffee, it is a sign of decline,” said Museveni. “It means you are unable to attack a real military target.”

Al-Shabaab depends on several different sources of income, including revenues from piracy, kidnapping and extortion, as well as funding from private donors overseas, particularly in the Gulf. Somalia’s president believes the recent attacks may be attempts to impress those benefactors whose largesse is all the more important after al-Shabaab lost control of the southern port of Kismayo – and with it the city’s lucrative charcoal trade – following an Amisom operation there last year. “The reason why al-Shabaab is carrying out these isolated attacks in Somalia and elsewhere is that they are losing the ground but they have to demonstrate to their supporters that they are still alive and they are still operating,” says Mohamud. “When they fail on the military front, they continue with these tactics.”

But a UN Security Council report in July painted a rather different picture. “The military strength of al-Shabaab, with an approximately 5,000-strong force, remains arguably intact in terms of operational readiness, chain of command, discipline and communication capabilities,” it said. “By avoiding direct military confrontation, it has preserved the core of its fighting force and resources.”

Charcoal trade
According to the UN report, al-Shabaab retains a hand in the charcoal trade in Kismayo and other southern ports like Barawe, which it controls. The UN estimated charcoal exports from Barawe alone are worth millions of dollars each month to the group. Barawe is where US commandos were last month forced to abort an operation aimed at capturing a senior al-Shabaab leader. Washington, fearful al-Shabaab could mount an attack on US soil, has provided funding, training and logistical support to Amisom in addition to carrying out its own special forces operations including drone strikes.

President Mohamud rejects the suggestion that the botched Barawe raid amounted to a propaganda coup for al-Shabaab. The group has been crowing about the Americans’ retreat on social media. He claimed its leaders based in the city had “run away” after the operation. “It gave a signal to al-Shabaab that they are not safe anywhere in Somalia,” he says.

An al-Shabaab attack on a UN base in Mogadishu in June, in which 22 people died, shook the international presence in the capital. “They are determined to destabilise the international effort and scare the international community away,” says Kay, the UN envoy. “It is not really surprising when they are pushed back and under pressure . . . We have taken as many security precautions as we can. The sense we need to be here and should be here remains.”