IT HAS been a rough decade for al-Qaeda. America and its regional allies assassinated its top leaders from Yemen to Iraq, and made it harder for the group’s branches to communicate with the central leadership. In 2011 America killed Osama bin Laden, its chief. Since Islamic State (IS) emerged a year later it has outflanked al-Qaeda, attracting more foreign fighters, cash and headlines. But one branch is an exception. Al-Qaeda in the Arabian Peninsula (AQAP), based in Yemen, is on the up. In the past month or so it has widened the territory under its control, including a port and an airport.

An interactive guide to the Middle East's tangled conflicts Today’s war in Yemen between the Houthi rebels and the government, backed by a Saudi-led coalition, is helping AQAP. It expanded after the ousting of Ali Abdullah Saleh from the presidency in 2012, only to be pushed back by an army offensive. But the government’s gains have now been reversed. On April 2nd AQAP freed members of its group from a prison. It took Mukalla, a port on the Gulf of Aden, and its nearby airport. American drone attacks, which previously kept AQAP on the back foot, have almost stopped since the Americans pulled out their intelligence-gathering special forces in the past few weeks.

Wherever it is based, AQAP’s main target remains the “far enemy” in America and Europe. It has not been able to carry out a big attack like 9/11, and few think any al-Qaeda branch could do so again, since the West has become more vigilant. But AQAP claimed the shooting at Charlie Hebdo in Paris in January. Though the group is unlikely to have been involved in the nitty-gritty of planning, at least one of the two gunmen had trained in Yemen. AQAP has had more success in hitting sites in the region, including embassies and tankers. In 2009 it narrowly failed to assassinate Muhammad bin Nayef, Saudi Arabia’s interior minister. More worryingly, it retains sophisticated bomb-making skills.

Nasser al-Wuhayshi, AQAP’s head, is the deputy leader of the whole organisation. Young and sparky, he and his group remain more popular among jihadists than Ayman Zawahiri, al-Qaeda central’s ageing chief. As IS is pushed back by the American-led coalition, al-Qaeda may come back into its own. Though a group calling itself IS carried out two bombings this year in Sana’a, Yemen’s capital, IS has no recognised branch in Yemen. “AQAP is still seen as potent,” says Bruce Riedel, a former CIA man now at Brookings, a think-tank in Washington. America recently increased its reward for information leading to Mr Wuhayshi’s arrest to $10m. That matches the bounty for IS’s chief, Abu Bakr al-Baghdadi, the world’s foremost terrorist.