One question above all others preoccupies Middle East analysts right now. It goes something like this. What do Saudi Arabia, the United States and Israel have in common? The answer, most conclude, is a shared hatred of Iran.

Caught right now in the crosshairs of this antipathy is another Middle East country. One that so often in the past has been a pliant arena for the proxy wars of global and regional powers. That country is Lebanon.

This weekend US Secretary of State Rex Tillerson is at pains to warn other countries against using Lebanon for proxy conflicts following a crisis triggered by the resignation of its prime minister, Saad Hariri.

“There is no legitimate place or role in Lebanon for any foreign forces, militias or armed elements other than the legitimate security forces of the Lebanese state,” Tillerson said.

While Tillerson might be trying to steady the regional boat, his commander-in-chief and US President Donald Trump however, seems determined to navigate in an altogether different direction.

Before examining Trump’s own reasoning and motives though, it’s important to recognise the wider backdrop against which Tillerson’s concerns about Lebanon are being played out.

In short, it’s that great Middle East rivalry between Saudi Arabia and Iran, the two Middle East giants that have long sat on either side of the Sunni-Shia divide, underpinning so much of the current conflict in the region.

This latest crisis in Lebanon however really has everyone on edge, heading as it might very well do towards the kind of all out regional religious war between Sunnis and Shias that most have long feared.

As ever with the Middle East those lining up on either side of this potential conflagration and the nature of their alliances and relationships is complex, at times even labyrinthine.

But easily the most significant factor by far has been the convergence of policy aims among Saudi Arabia, the United States and Israel. All three want to roll back Iran's reach in the region, and in doing so are focusing much of their attention on Hezbollah the powerful political party and militia that has long been Iran’s ally in Lebanon.

The fast-paced events of the past week leading to the crisis in Lebanon come of course in the wake of a shake-up in Saudi Arabia under the leadership of Crown Prince Mohammed bin Salman - also known as MbS.

Dramatic change is in the air in the desert kingdom. Last week in a power grab by MbS dozens of Saudi princes, senior military officers, businessmen and top officials, including a well-known royal billionaire with extensive holdings in Western companies, were arrested as part of a sweeping purported anti-corruption probe that further cements control in the hands of the young crown prince.

The purge followed a visit to Saudi Arabia last month by Jared Kushner, Donald Trump’s son-in-law, who reportedly stayed up half the night discussing strategy with the crown prince. This cosying up between the House of Saud and the House of Trump has taken on a fresh impetus of late.

“I have great confidence in King Salman and the Crown Prince of Saudi Arabia, they know exactly what they are doing,” Trump tweeted following the purge.

Beyond a mutual liking for golden elevators, both Trump and MbS see eye-to-eye on many things, not least their dislike and antipathy towards Iran.

Some observers believe that from the outset of Trump’s presidency the Saudis and MbS turned his visit to the desert kingdom - the president's first foray outside the United States - into a veritable love fest and string of hyperboles.

It was a place in which Trump says he cut “tremendous” deals and expressed his pride in the new relationship and the “like-minded” goals the two nations share.

Not surprisingly many Middle East observers see the headstrong combination of Trump and MbS as a real cause for concern.

“Most troubling for the regional stability-or-chaos picture is the flagrant inexperience and lack of nuance among the new US and Saudi leaders,” observes veteran Middle East writer Rami Khouri, professor of journalism at the American University of Beirut.

“President Donald Trump and Prince Mohammed both use bravado, threats and military force to show their resolve and assert their political manhood,” Khouri warns.

It’s all a far cry from the days when Washington found itself constantly frustrated by Saudi Arabia’s inaction and caution. A mood once summed up somewhat colourfully during the Gulf War by former US Secretary of State James Baker, who quipped that the Saudi leadership “could f… up a two car funeral”.

Those days though are long gone and right now Saudi Arabia has become what America always wanted it to be and maybe, say some analysts, a lot more than Washington has bargained for.

“King Salman and Mohammed bin Salman seem to have set a new land speed record in convincing the Trump administration that they hold the keys to war, peace, and the transformation of the region,” was how analysts Aaron David Miller and Richard Sokolsky summed it up recently in the influential current affairs magazine Foreign Policy. Saudi policies, both domestic and foreign, have become increasingly aggressive under MbS. In addition to his power grab, he’s escalated Saudi involvement in Yemen, continued his boycott of Qatar, ostensibly another American ally, and is now making inflammatory statements about Iran.

The trigger for the latest Lebanon crisis was the sudden resignation last week, while in Saudi Arabia, of Lebanese Prime Minister Saad Hariri. It was a decision made, he said, mainly because he saw Hezbollah and Iran as threats to the country that made his job impossible. But in Lebanon itself and elsewhere, Hariri’s decision was interpreted very differently, and regarded as a purely Saudi decision that was forced on him. Some Lebanese analysts point out that the Saudis have always treated the Hariri family, who have been bankrolled by Riyadh for decades, almost as a wholly owned subsidiary.

Since Hariri’s resignation while in Saudi Arabia, rumours of his virtual kidnapping have rocked the Arab world. Many Lebanese officials remain convinced that such moves by MbS is his way of forcing their country into Saudi Arabia’s confrontation with Iran. Tensions escalated even further on Friday when Saudi Arabia ordered its citizens to leave Lebanon immediately.The Saudi order for its citizens to leave, also made by the kingdom’s allies in Bahrain and Kuwait, came after the country’s foreign minister, Adel al-Jubeir, said his government would treat Lebanon as a hostile state as long as Hezbollah was in the government. He described Hezbollah’s participation in government as an “act of war” against Saudi Arabia.

As a New York Time editorial on the same day highlighted, Trump’s reaction to all of this has been “no problem” - and he continues to make clear that he sides with the House of Saud and its Sunni allies against Shi’ite-led Iran. “If Washington is not careful, the Saudis will sandbag America into standing up to Tehran while the Saudis hide behind its skirt,” warned Aaron David Miller in his Foreign Policy magazine analysis last week.

Trump’s uncritical support of MbS has not surprisingly stirred fears of an all out war with Iran that most likely would be played out on Lebanese soil where its powerful regional ally Hezbollah has its base. Trump’s unflinching support for MsB has also pitched the US leader into a totally opposing position from that of his Secretary of State. Rex Tillerson’s statement on Friday cautioning against using Lebanon for proxy conflicts was a stern if indirect, admonishment to Saudi Arabia, and to his boss in the Oval Office. But if Trump and MbS seem hell-bent on going their own way in turning the screw on Iran, then the third partner in the anti-Tehran triumvirate is Israel.

At face value Israel might seem an unlikely ally of Saudi Arabia. Saudi Arabia and Israel have no diplomatic ties and successive Saudi leaders have said that will not change unless a settlement is reached with the Palestinians.

But their growing closeness and alliance is a typical example of that familiar old Middle East maxim that “the enemy of my enemy is my friend”.

Allegations of a pact, at least on a de-facto level, between Saudi Arabia and Israel were given new impetus after it was revealed that Israeli diplomats were asked to repeat talking points, almost identical to remarks made by Saudi leaders after the Hariri resignation claiming Hezbollah had made his job impossible.

As Bessma Momani a senior fellow at the Centre for International Governance and Innovation, wrote recently, Israel’s “mow the lawn” approach to contain Hezbollah via periodic wars to reduce its military capacity means that Israel itself is likely due for conflict with Lebanon.

Momani says that the politically bruised Prime Minister of Israel, Benjamin Netanyahu, would like nothing more than to have a conflict to rally his people around and divert attention away from troubling corruption charges against him and his wife, and there is little doubt Israelis are pushing the Saudis to confront Hezbollah and Iran hard.

On Thursday Israeli intelligence minister, Yisrael Katz, said he believed conditions were ripe for a diplomatic offensive against Iran and Hezbollah at the United Nations, where he said Israel would seek better enforcement of a 2006 ceasefire agreement that called on Hezbollah to disarm and stay away from its border.

Overall Israel’s political and military leadership appears to have concluded that a conflict with Hezbollah is becoming increasingly likely, despite months of growing warnings that what would be their third Lebanese war would be more dangerous and deadly than the last conflict in 2006.

For its part Hezbollah’s response has been unequivocal. The group’s leader Hassan Nasrallah said on Friday that Riyadh is inciting Israel to strike Lebanon, and his militant group is watching carefully for any Israeli attempts to use the crisis to begin hostilities against Lebanon.

“I warn them against any miscalculation or any step to exploit the situation,” he said. “Today we are more confident and feeling stronger in the face of any threat,” insisted Nasrallah.

The Hezbollah chief has every reason to feel such confidence. Hezbollah’s forces appear to be emerging from the Syrian war as a battle-hardened and largely conventional military force whose missiles have been heavily resupplied by Tehran despite dozens of Israeli airstrikes on convoys and depots of late.

Israel whose much vaunted military took something of a bloody nose during its last conflict with Hezbollah in 2006 would no doubt this time bring its full might to bear.

Already top Israeli military and political figures have detailed the probable shape of a future conflict, with air force chiefs suggesting that Lebanon could be subjected to a huge aerial bombardment in the opening days of a campaign resulting most likely in a high number of civilian casualties.

And so the region once again finds itself poised on a knife-edge. In the eyes of the triumvirate, Saudi Arabia the United States and Israel, Iran and its ally Hezbollah in Lebanon have become dangerous principal actors in need of cutting down to size quickly and decisively.

While Israel would at some point always be compelled to confront Hezbollah, a headstrong young Saudi prince and a blustering US president are now adding momentum and putting the region on a collision course towards another war.

A war that even by current Middle East standards could be much more wide ranging.

Sitting above all this is Donald Trump at odds with his own Secretary of State and seemingly oblivious to the choices he’s making.

“He’s banked US credibility, image, and policy on a young kid whose ambitions and drive seem to have outstripped his wisdom, experience, and judgment,” was how analysts Aaron David Miller and Richard Sokolsky summed up this now incredibly dangerous crisis.

“Mohammed bin Salman is up on a tight wire… the president, without thinking any of this through, has got America and the future of the region up there with him.”