In southern Somalia, internecine fighting erupted after dark on 19 June, and it was merciless, the villagers said. Rival factions divided by personal, clan and ideological differences opened fire with automatic weapons in Barawe, in the Lower Shabelle region. The locals cowered in their homes as the bullets flew.

Trouble had been brewing for months. But once the shooting started, there was no going back. Within days, al-Shabaab, Somalia's most feared Islamist militia and western-designated terrorist group, had split. The nationalist wing was routed, and the so-called global jihadists, led by the group's hardline emir, Ahmed Abdi Godane (aka Sheikh Mukhtar Abu Zubeyr), had taken control.

The brutal coup confirmed Godane's position as al-Shabaab's pre-eminent leader, but it was clear he must demonstrate his power if his control of al-Shabaab was to endure, analysts suggested. He needed a big operation to make his mark. Thus it was that the June shootout, boosting Godane's power and paranoia, led directly to the Westgate attack in Nairobi, for which al-Shabaab has admitted responsibility.

After Westgate, Godane has emerged as Africa's most wanted man and, perhaps, its most hated. Once the dust settles in Nairobi, the immediate focus will shift to the al-Shabaab perpetrators of the atrocity – and the hunt for Godane will be on.

One of the founder members of al-Shabaab, Godane was born in July 1977, in Hargeisa, Somaliland, and belongs to the Isaaq clan. He studied at a madrassa in Pakistan on a Saudi-funded scholarship, and is said to be an Afghan war veteran. He returned to Somalia in 2001.

After working in 2006 as secretary-general of the Islamic Courts Union, a more moderate predecessor to al-Shabaab, Godane rose steadily in the increasingly militant militia after the ICU was suppressed. He became emir in 2008 after his predecessor was killed in aUS air strike. That year the US named him a "specially designated global terrorist", and in 2012 placed a $7m bounty on his head.

According to Nathaniel Horadam at the American Enterprise Institute, Godane is a shadowy figure who keeps a low profile: "His ideological upbringing and theological beliefs place him as the central figure in al-Shabaab's takfir wing. A 2010 International Crisis Group report described him as uncharismatic and reclusive. He makes the majority of his statements in recorded audio messages distributed through online jihadist forums."

Unconfirmed Somali media reports say that Godane has a home in Sharjah, in the United Arab Emirates, where his wife and children have lived since 2008. The reports also claims he visited them twice in 2010, using a Kenyan passport with a different name to enter the country.

In his first statement as head of al-Shabaab, Godane pledged allegiance to Osama bin Laden and vowed to launch a direct attack on the US. He has consistently rejected negotiations with what he terms Somalia's "apostate government", arguing that it must either surrender or face destruction. In 2012, completing his personal ideological journey to the violent extreme, he formally affiliated al-Shabaab to al-Qaida. Godane has since expressed solidarity with the Islamic State of Iraq, an al-Qaida franchise. And he claimed responsibility for the 2010 World Cup bombings in Kampala that killed 74 people, a strike mounted in retaliation for Uganda's participation in the Amisom peacekeeping mission in Somalia.

That attack now looks like a precursor of the Nairobi atrocity. But he was clear about his intentions all along. "What happened in Kampala was just the beginning," Godane warned.

Adjoa Anyimadu, research associate at the Chatham House thinktank's Africa programme, said it was all but certain that Godane masterminded the Westgate attack, and that a massive manhunt for him would ensue. But he would also have to watch his back.

"Godane has been consistently at the top of al-Shabaab and he has been consolidating his position since June. But I never cease to be surprised at their internal wrangling. These people are not shy about killing each other. So Godane's ascendancy may not last," she said.

Anyimadu said she believed the international community – both western and African Union countries – would be forced to take a more realistic view of al-Shabaab after Westgate, given this latest demonstration of the group's ability to mount large-scale operations beyond Somalia's borders.

"I think they will have to pay more attention to the internal dynamics of al-Shabaab and how it has evolved since it was forced out of Mogadishu two years ago."

Anyimadu suggested that Ethiopia, which invaded Somalia in 2006 with US support to crush the Islamic Courts Union, might also become more actively involved again. Ethiopia already has troops positioned inside the country, along the shared border.

In that case, and given the pressure for increased western and African Union action, it is possible the Westgate atrocity could lead to a far broader, regional escalation of the Horn of Africa conflict – a result the ruthless global jihadist Godane would undoubtedly welcome.