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Early on 5 June, Saudi Arabia, the UAE, Bahrain and Egypt cut diplomatic ties with Qatar, along with the closing of all land, sea and air communications, accusing Doha of supporting terrorism.
The actions were matched later in the day by the Maldives, the Saudi-backed, internationally-recognised government in Yemen, and by one of the governments in Libya.
It is as shocking a development as it is significant.
MEED Exclusive on Qatar crisis
Doha has a history of pursuing a foreign policy agenda that is at odds with its regional neighbours and as a result, it has a history of falling out with its neighbours, particularly Saudi Arabia.
In 2014, the same countries severed diplomatic ties over concerns about Dohas support for non-state actors the Muslim Brotherhood in Egypt and the Al-Nusra Front in Syria.
Earlier, in 2002, fed up with what it saw as meddling in regional affairs by its jumped-up, diminutive neighbour, Riyadh severed diplomatic relations with Doha. It took six years for the ice to thaw.
But the severity of the actions taken in early June by Qatars closest neighbours and allies has elevated the situation to an unprecedented level that could have far-reaching and damaging consequences for both Qatar and the GCC.
The action has exposed a previously unknown degree of distrust among the six-nation GCC bloc, which was set up in 1981 as a security bloc to counter the perceived threat of Iran.
Doha is being forced to change its ways.
Tensions between Qatar and its GCC partners have risen over the past month, following comments reported to have been made by Qatars Emir Sheikh Tamim bin Hamad al-Thani, in which he is alleged to have expressed support for Iran, Hamas and the Muslim Brotherhood, and criticised the US.
Qatar has denounced reports of the comments as fake news. It also said a report by the states official news agency that said Qatar had recalled its diplomats from Saudi Arabia, the UAE, Egypt and Bahrain, was the result of a cyber attack.
But the actions on 5 June reveal Qatars GCC partners are not buying it.
Isolated and vulnerable
While Sheikh Tamims alleged comments in themselves are not the cause of the blockade, they are seen as reflecting Qatars true policies, and its allies are saying enough is enough.
Doha denies strenuously the accusations, but the action leaves it isolated and vulnerable, and the emir exposed.
Sheikh Tamim is playing to a domestic audience, a large proportion of which is unhappy at some of his modernisation policies, and many of whom support the views that Qatar is accused of.
But the country is dependent on outside support and the blockade leaves it with limited room for manoeuvre and boxed into a corner.
The consequences of resisting the call for change for too long could be catastrophic for Qatar.
With more than 40 per cent imported from Saudi Arabia and the UAE, the country faces serious disruption to its food supplies.
Iran is reported to have said it can step in to supply the small, peninsular state with food supplies at short notice. But such a step would risk escalating the crisis further.
Imports of construction materials needed to deliver its World Cup and infrastructure schemes will also be hit, pushing up costs and adding delays to the projects.
Meanwhile, Qatars vision of becoming a travel and tourism hub in the region will be undercut by the transport restrictions.
It is difficult at this stage to see any resolution to the crisis that does not involve major concessions from Doha.