NINETY years ago, Britain’s planes bombed unruly tribes in the Arabian peninsula to firm up the rule of Abdul Aziz ibn Saud, the founder of the Saudi state. Times have changed but little. Together with America and France, Britain is now supplying, arming and servicing hundreds of Saudi planes engaged in the aerial bombardment of Yemen.

Though it has attracted little public attention or parliamentary oversight, the scale of the campaign surpasses Russia’s in Syria, analysts monitoring both conflicts note. With their governments’ approval, Western arms companies provide the intelligence, logistical support and air-to-air refuelling to fly far more daily sorties than Russia can muster.

There are differences. Russian pilots fly combat missions in Syria, whereas Western pilots do not fly combat missions on behalf of the Saudi-led coalition in Yemen. Nor are their governments formal members of the battling coalition. Their presence, including in Riyadh’s operations room, and their precision-guided weaponry, should ensure that the rules of war that protect civilians are upheld, insist Western officials. But a series of recently-published field studies question this. Air strikes were responsible for more than half the thousands of civilian deaths in the 16-month campaign, Amnesty International reported in May. It found evidence that British cluster bombs had been used. Together with other watchdogs, including the UN Human Rights Council, Human Rights Watch and Oxfam, it has documented the use of Western weaponry to hit scores of Yemeni markets, medical centres, warehouses, factories and mosques. One analyst alleges Western complicity in war crimes.

The war in Yemen has certainly been lucrative. Since the bombardment began in March 2015, Saudi Arabia has spent £2.8 billion on British arms, making it Britain’s largest arms market, according to government figures analysed by Campaign Against Arms Trade. America supplies even more.

Western support might have helped reduce Saudi Arabia’s ire at the nuclear deal America and other world powers signed easing sanctions on Iran. But it has also fuelled another conflict in the Middle East. Together with the ground war and the Saudi-led blockade, it has devastated infrastructure in what was already the Arab world’s poorest country, displaced over 2m people and brought a quarter of Yemen’s population of 26m to the brink of famine. Aid agencies warn that another refugee exodus across the Red Sea and on to the Mediterranean could be in the offing.

Negotiations aimed at ending the war resumed on July 16th in Kuwait. But both sides have scoffed at Kuwait’s threats to expel their delegations if they fail to conclude a deal within two weeks. Yemen’s president-in-exile, Abd Rabbo Mansour Hadi, who hopes to install his own government, has dismissed the UN envoy’s proposals for a power-sharing administration. He has shored up his own team with hardliners. A civil war in the 1960s, note observers gloomily, lasted eight years.

The bombardment has dented the fighting strength of Saudi Arabia’s foes—the remnants of the Yemeni Republican Guard under the former president, Ali Abdullah Saleh, and the Houthis, a northern Shia militia. But it has failed to break the deadlock or expel them from Yemen’s capital, Sana’a. Despite the bombastic pledge of Mr Hadi to “be in the capital soon”, fighting continues around Ma’arib, 120km (75 miles) from it.

A fragmenting country further complicates the peacemakers’ task. Southerners in the port city of Aden are increasingly seeking to resurrect a separate state. Further east, Gulf states led by the United Arab Emirates have struck at al-Qaeda’s build-up in Hadramawt, fearful of a spillover into their own states which have large Yemeni populations. Recent bombings in the Saudi cities of Medina, Jeddah and Qatif underscore the reach the jihadists already have.

As the war drags on, nervousness grows. President Barack Obama banned the dispatch of cluster bombs in April, though Congress later reinstated it. The Gulf states too seem increasingly unnerved by the costs. Had but a fraction of Saudi’s $87 billion defence budget gone on development in Yemen, says a long-time Gulf observer, the deployment could have been of consultants with pens in their pockets.