F OR MONTHS General Khalifa Haftar, Libya’s most powerful warlord, has besieged Tripoli, struggling to wrest control of the capital from the UN -backed “government of national accord” ( GNA ). More than 1,000 people have been killed. Mr Haftar is aided by Emirati and Egyptian air strikes. But the lines hardly move. A little-known group of Salafists (ultra-conservative Muslims) called the Madkhalists may yet tip the balance.

Under orders from their leader, an octogenarian Saudi preacher named Rabee al-Madkhali, the Madkhalists outside the capital have joined Mr Haftar’s ranks, while those inside encourage fighters to give up. “Put down your weapons, go home, pray and read the Koran,” says Fahmy Naas, a follower in Tripoli. War is fitna (strife or sedition), he insists.

The Madkhalists make up less than 10% of Libya’s people. Those with guns number between 8,000 and 25,000. The GNA ’s commanders blame the group for undermining morale. They say Madkhalists in Tripoli are in regular contact with their brethren on Mr Haftar’s side and constitute a fifth column. “If Haftar breaks into the capital, the Madkhalists will bring their supporters cheering onto the streets,” says an official in Tripoli.

Madkhalism took root in Libya under Muammar Qaddafi. Unlike Libya’s other Islamists, the Madkhalists shunned the Arab spring of 2011, when Libyans toppled the old dictator. Their support then shifted to Mr Haftar on the basis of ghalaba, the principle that God makes the rightful leader win. The wali al-amr, or rightful leader, Mr Madkhali insists, is wali al-aqwa, the strongest one.

The Madkhalists make strange bedfellows of Mr Haftar, who claims to be fighting Islamist terror. In Libya’s east, which he rules, they have been handed control of the religious-affairs ministry. From their pulpits they order women indoors and stage book burnings.

They have also stoked sectarian tension by destroying the shrines of Sufi mystics and declaring Ibadism, the sect of Libya’s Berber minority, heretical. Their henchmen have beheaded defiant sheikhs and killed confidants of Libya’s grand mufti, who supports the GNA .

But the Madkhalists earned the gratitude of many Libyans by restoring order to neighbourhoods after the collapse of Qaddafi’s regime. Many young men have been drawn to their simple politics. Mr Madkhali tells followers to show unflinching obedience to the wali al-amr.

Saudi Arabia is suspected of financing the Madkhalists, who helped Mr Haftar defeat Islamist fighters in Benghazi and turf Islamic State out of Derna, farther east. In Tripoli the Madkhalists man the Special Deterrence Force, or RADA , which controls the airport. They have mostly stayed out of the fight with Mr Haftar.

Some fear the Madkhalists might turn into something like al-Qaeda. “You can’t use people and guarantee that they won’t go off-track,” says a Salafist politician in Egypt. “People are not machines.”