It began as a squabble between Arab allies, but the standoff between Qatar and its neighbours is threatening to engulf the Horn of Africa. When Saudi Arabia, the United Arab Emirates, Egypt, Bahrain, Yemen and the Maldives declared at the beginning of June that they were severing diplomatic relations with Qatar it appeared to be of interest mainly to the Arabian Peninsula - and the Gulf in particular.
The Saudis and their allies accused Qatar of backing international terrorism. The US, which has the Al Udeid air base in Qatar, looked askance, but did little more than use its good offices to try to ensure that the war of words did not flare into an open conflict.
But the countries just across the Red Sea have found themselves dragged into the dispute. After prevaricating for some time, Eritrea, which had hitherto good relations with Qatar, fell into line with the Saudis and broke ties with Qatar.
A statement attributed to the Eritrean government declared limited support for the rupture with Qatar. Eritrea explained that the initiative taken by the Gulf nations
is among many in the right direction that envisages full realisation of regional peace and stability.
Matters might have ended there, but such are the ties between nations on both sides of the Red Sea that this was unlikely. The UAE and Saudi Arabia have been using the Eritrean port of Assab in their war against the Houthi rebels in Yemen. Egypt - which is part of the Saudi alliance - is also reported to have plans to build a major base on an Eritrean island in the Red Sea. The Eritreans are alleged to have some 400 troops fighting against the Iranian backed Houthis.
In the circumstances, a rupture between the Saudi alliance and Qatar was highly likely to spread to the Horn. And this was exactly what took place. Qatar had been a generous donor to Eritrea. It had also played a key mediating role in Eritrea's border conflict with Djibouti, which flared in April 2008.
The origins of the disputed border lie buried in the sands of colonial history and would never be easily resolved.
Qatar pull-out stokes tensions
The fighting left a number of Djibouti troops as prisoners of war in Eritrea and Qatar did their best to resolve this issue by mediation. Indeed, so close were the ties that when UN monitors met the political advisor to the President of Eritrea, Yemane Gebreab, in January 2013 and enquired about the Djiboutian prisoners of war, he responded that
all matters concerning the resolution of the conflict with Djibouti could only be addressed through the mediation of Qatar, and that no other intermediary was necessary.
Qatar went further, deploying some 200 of its own troops along the Eritrea-Djibouti border in an attempt to reduce the tension. The Qatari peacekeeping force only supervised a small sector of the border near Ras Dumeira. It was therefore not in a position to observe or interdict cross-border movements further to the south, but its presence was symbolically important.
So when Qataris pulled their troops out on June 12th and 13th, there was something of a vacuum, which Eritrea is reported to have promptly filled. Djibouti accused the Eritreans of moving their troops into the disputed territory. Djibouti's Foreign Minister Mahamoud Ali Youssouf declared that his country's military had gone into "alert".
A senior Eritrean diplomat at the African Union said the move came after Eritrea cut diplomatic ties with Qatar and his country sought no confrontation with Djibouti.
But a terse statement from the Eritrean Ministry of Information issued days later described Qatar's withdrawal as "hasty". It said Eritrea had refrained from commenting because it was not privy to the action but would do so once it had all the information about the event.
The African Union, seldom swift to comment or intervene in any disputes effecting its members, finally made a move. Moussa Faki Mahamat, chairperson of the African Union Commission, tweeted that the AUC would send a delegation to Djibouti border to monitor developments and work with all parties.
More uncertainty for The Horn
These events appear to have fallen well for Ethiopia, which has been at loggerheads with Eritrea since their own border war of 1998-2000. While Eritrea and Djibouti are daggers drawn following the Qatari withdrawal, Ethiopia has refrained from taking sides between the Saudis and Qatar. Both parties have sent delegations to Addis Ababa, no doubt asking for Ethiopian support, but so far Ethiopia has sat on the fence.
Ethiopia recently announced that it would reveal a new policy towards Eritrea, but none has appeared to date. With its troublesome northern neighbour locked in a fresh controversy with Djibouti, Ethiopia may find it's more likely to receive a sympathetic hearing for any initiative from the international community.
It will not be difficult, for instance, for Addis Ababa to portray Eritrea as a regional troublemaker, always willing to exploit a neighbour's weakness. It should not be forgotten that since independence in 1993 Eritrea has been involved in conflicts with Yemen, Djibouti and Ethiopia - hardly a proud record.
The UN and the African Union are now engaged in trying to mediate between Eritrea and Djibouti. Meanwhile, the ongoing conflict in Yemen continues to have implications for the Horn, as the Saudis and UAE continue to use Eritrea as a rear base. The UAE is in fact seeking a further base in nearby Somaliland.
As ever, it's difficult to predict how events will unfold, but sparks from Arabia can easily set the Horn alight.
Martin Plaut is affiliated with the Institute of Commonwealth Studies of the University of London, the Royal African Society and Chatham House