Aren't Qatar and Saudi Arabia on the same side?

You could certainly be forgiven for thinking so. Both countries are fabulously wealthy absolute monarchies built on petrodollars, both have strong relations with the United States and other Western countries and both are ruled by Arab dynasties which, like the majority of their citizens, are conservative Sunni Muslims. When Saudi Arabia announced its Operation Decisive Storm intervention in Yemen in 2015, Qatar was one of the 33 Asian and African allies it named in its coalition.

So why the sudden split?

The answer is that there is nothing sudden about it. For many years Qatar has harboured its own ideas about the future of the Middle East, ideas that have irritated the Saudis and at times directly contradicted them. Riyadh and two other Gulf monarchies - Bahrain and the UAE - froze diplomatic ties with Qatar in March 2014, but this week's split is of a different order of magnitude, involving the closure of borders, cessation of trade and withdrawal of their citizens. It has even been reported that Qataris are to be forbidden from transiting through airports in neighbouring countries.

Three incidents appear to have sparked the latest escalation:

• Donald Trump's first foreign trip as US president to the Saudi capital Riyadh, during which he issued a ringing endorsement of Saudi leadership and made it clear that Washington's chief adversaries in the region were terrorism and Saudi Arabia's chief regional rival, the Islamic Republic of Iran;
• The subsequent publication on the website of Qatar's state news agency of comments attributed to the emirate's ruler, Sheikh Tamim bin Hamad al-Thani, that criticised plans to isolate Iran and suggested that Trump may not be president for much longer - comments that Qatari officials insist were fake and placed on the site by hackers;
• Qatar's April payment of a massive ransom - reputedly as much as $US1 billion in total - to secure the release of Qatari nationals, said to include members of the royal family, from captivity in Iraq. The beneficiaries reportedly include Iran and its Shiite militia proxies in Iraq and Sunni Islamists fighting in Syria who are linked to al-Qaeda.

What are the Saudis accusing Qatar of?

In a nutshell, supporting terrorism. A pretty serious charge for a nation that was invited to attend the Trump visit, has been fighting alongside the Saudis in Yemen and is scheduled to host the 2022 World Cup.

Is it true?

As those who have followed the Syrian war will know, the Assad regime regards all current opposition to its rule as terrorism. Turkish President Recep Tayyip Erdogan has declared major parties in Turkish life to be terrorist movements and the Egyptian regime has banned the Muslim Brotherhood on the basis that it is a terrorist group trying to destroy the nation. The surrounding Arab states use similar rhetoric when dealing with dissent and violence of all kinds, so the charge of terrorism has become an extremely broad one that even takes in media, such as the Qatari-owned television network al-Jazeera.

Qatar certainly supports opposition groups in the Arab world that the Saudis would like to disappear. It has also supported militias fighting in Syria who have extreme Islamist positions - though the Saudis might also be accused on this count. But evidence of Qatari state support for the kind of terrorism that has rocked Western cities in recent weeks is scant.

As for al-Jazeera, if reporting the positions of those critical of the state or opposed to the state is to be considered terrorism, then Peter Greste and his colleagues would also fall foul of the charge.

US Defence Secretary Jim Mattis meets Saudi King Salman in Riyadh in April to discuss the situation in Yemen. Photo: US Department of Defence via New York Times

So why are some countries joining the Saudi bandwagon?

The rulers of Saudi Arabia and Qatar belong to the same endangered species: jet-setting autocrats. Their differences go back to the upheavals of the so-called "Arab Spring" of 2011 and 2012. The question those upheavals raised was how to keep the wolf from the door - the "wolf" being their own citizens' demands for greater representation and a role in determining their countries' futures.

The Saudis believed from the outset that the Tunisian and Egyptian and Bahraini regimes should be upheld and that dissent should be crushed using the state's security forces or bought off using targeted state spending. They also believed that Iran should be isolated and rejected in much the same way that the US had for decades isolated and rejected Cuba and North Korea. When the Obama administration departed from these positions they were shocked and dismayed, and the relationship never recovered. They have since rallied by intervening militarily in Yemen and Bahrain, funding the return of military rule in Egypt and backing a general in Libya.

The Qataris, by contrast, appeared to believe that the key to the survival of the Gulf monarchies was to try and find a political ally within the mass protests and make a deal with them as a hedge against democrats, leftists and others, including jihadists bent on deposing them. From the Qatari perspective the best allies would be parties that represented political Islam, such as the Muslim Brotherhood in Egypt, Hamas in Palestine and the AKP in Turkey.

What are other countries saying about this?

For the moment, as little as possible. Australia - to cite a fairly typical example - has substantial trade and military ties with the Saudis but is also very keen to do business in Doha. US Secretary of State Rex Tillerson has also tried to walk a middle path, offering to help broker a deal between the two sides. For poorer Asian nations with hundreds of thousands of migrant workers in the relevant countries, the hope is that it will all blow over. The March 2014 dispute lasted nine months.

The one Western politician who seems to be keen to accentuate the row is Donald Trump, with a steady stream of tweets citing it as evidence of his own positive influence in the region.

Hamas leaders and supporters in Gaza City listen to Khaled Mashaal, the outgoing Hamas leader, launch a new manifesto from Doha, Qatar, in May. Photo: AP

So what is likely to happen next?

The Saudis will certainly be hoping that Qatar climbs down and agrees to curb al-Jazeera - something it has done before to get its neighbours off its back. But they also want Doha to accept Riyadh's leadership and to agree to Saudi positions on Libya, Syria, Egypt, the Israeli-Palestinian conflict (where the Palestinian Authority under Mahmoud Abbas is preferred to its Hamas rivals) and above all to take a harder line towards Iran. They also want Qatar to stop using its role as a broker to raise its political profile above Saudi Arabia's, as it has in Lebanon and Afghanistan.

Qatar will hope that the international community has an interest in defusing this dispute and that it will be able to find a way to restore ties without losing face. As he reads the tweets from the White House, Sheikh Tamim - like Malcolm Turnbull after his first phone call with President Trump - will try to comfort himself with the knowledge that the US relies on Qatar as a crucial regional base, with 11,000 American troops stationed on Qatari soil, an arrangement that began when the Saudis asked US troops to leave.

Much will depend on how serious Donald Trump is about re-shaping the Middle East, and how much he is simply posturing.

Maher Mughrabi is the Foreign Editor of The Age and The Sydney Morning Herald.