In any case, the benefits of a US-Iran agreement may be slow to come, if they come at all, as the Republicans in Congress, the Saudis and Israel try to torpedo it. And even if an accord is ratified and implemented, President Obama could be hedged in by its opponents from further co-operation with Iran in other parts of the Middle East. In contrast to this snail’s pace rapprochement, the crises in Yemen and Syria are getting worse by the day and, in Iraq,for all the government’s claims to have captured Tikrit, its forces are still only nibbling at the outer defences of Islamic State (Isis).

Saudi Arabia and the Gulf monarchies have the greatest self-interest in maintaining the status quo in the region, something they have been fairly successful in doing in the past. Who would have predicted in the late 1950s that Arab nationalist and socialist movements would pass away but Saudi Arabia would remain the theocratic absolute monarchy it has always been? What is striking about developments in the past few weeks is that it is Saudi Arabia that is seeking radical change in the region and is prepared to use military force to secure it. In Yemen, it has launched a devastating air war and, in Syria, it is collaborating with Turkey to support extreme jihadi movements led by Jabhat al-Nusra, the al-Qaeda affiliate that last week captured its first provincial capital.

The Saudis are abandoning their tradition of pursuing extremely cautious policies, using their vast wealth to buy influence, working through proxies and keeping close to the US. In Yemen, it is the Saudi air force that is bombarding the Houthis, along with Yemeni army units still loyal to former president Ali Abdullah Saleh who was once seen as the Saudis’ and Americans’ man in Sanaa, the Yemeni capital. As with many other air campaigns, the Saudis and their Gulf Co-operation Council allies are finding that air strikes without a reliable military partner on the ground do not get you very far. But if Saudi ground forces are deployed in Yemen they will be entering a country that has been just as much of a quagmire as Afghanistan and Iraq.

The Saudis are portraying their intervention as provoked by Iranian-backed Shia Zaidis trying to take over the country. Much of this is propaganda. The Houthis, who come from the Zaidi tribes in Yemen’s northern mountains, have an effective military and political movement called Ansar Allah, modelled on Hezbollah in Lebanon. They have fought off six government offensives against them since 2004, all launched by former President Saleh, then allied to the Saudis. Saleh, himself a Zaidi but drawing his support from the Zaidi tribes around the capital, Sanaa, was a casualty of the Arab Spring in Yemen but still has the support of many army units.

Why has Saudi Arabia plunged into this morass, pretending that Iran is pulling the strings of the Shia minority though its role is marginal? The Zaidis, estimated to be a third of the 25 million Yemeni population, are very different Shia from those in Iran and Iraq. In the past, there has been little Sunni-Shia sectarianism in Yemen, but the Saudi determination to frame the conflict in sectarian terms may be self-fulfilling.

Part of the explanation may lie with the domestic politics of Saudi Arabia. Madawi al-Rasheed, a Saudi visiting professor at LSE’s Middle East Centre, says in the online magazine al-Monitor that Saudi King Salman’s defence minister and head of the royal court, his son Mohammed bin Salman, aged about 30, wants to establish Saudi Arabia as absolutely dominant in the Arabian Peninsula. She adds caustically that he needs to earn a military title, “perhaps ‘Destroyer of Shiite Rejectionists and their Persian Backers in Yemen’, to remain relevant among more experienced and aspiring siblings and disgruntled royal cousins”. A successful military operation in Yemen would give him the credentials he needs.

A popular war would help unite Saudi liberals and Islamists behind a national banner while dissidents could be pilloried as traitors. Victory in Yemen would compensate for the frustration of Saudi policy in Iraq and Syria where the Saudis have been outmanoeuvred by Iran. In addition, it would be a defiant gesture towards a US administration that they see as too accommodating towards Iran.

Yemen is not the only country in which Saudi Arabia is taking a more vigorous role. Last week, President Bashar al-Assad of Syria suffered several defeats, the most important being the fall of the provincial capital Idlib, in northern Syria, to Jabhat al-Nusra which fought alongside two other hardline al-Qaeda-type movements, Ahrar al-Sham and Jund al-Aqsa. Al-Nusra’s leader, Abu Mohammed al-Golani, immediately announced the instruction of Shia law in the city. Sent to Syria in 2011 by Isis leader Abu Bakr al-Baghdadi to create al-Nusra, he split from Baghdadi when he tried to reabsorb al-Nusra in 2013. Ideologically, the two groups differ little and the US has launched air strikes against al-Nusra, though Turkey still treats it as if it represented moderates.

The Syrian government last week accused Turkey of helping thousands of jihadi fighters to reach Idlib and of jamming Syrian army telecommunications, which helped to undermine the defences of the city. The prominent Saudi role in the fall of Idlib was publicised by Jamal Khashoggi, a Saudi journalist and adviser to the government, in an interview in The New York Times. He said that Saudi Arabia and Turkey had backed Jabhat al-Nusra and the other jihadis in capturing Idlib, adding that “co-ordination between Turkish and Saudi intelligence has never been as good as now”. Surprisingly, this open admission that Saudi Arabia is backing jihadi groups condemned as terrorists by the US attracted little attention. Meanwhile, Isis fighters have for the first time entered Damascus in strength, taking over part the Yarmouk Palestinian camp, only ten miles from the heart of the Syrian capital.

Saudi Arabia is not the first monarchy to imagine that it can earn patriotic credentials and stabilise its rule by waging a short and victorious foreign war. In 1914, the monarchs of Germany, Russia and Austro-Hungary had much the same idea and found out too late that they had sawed through the branch on which they were all sitting. Likewise, Saudi rulers may find to their cost that they have been far more successful than Iran ever was in destroying the political status quo in the Middle East.