Qatar's return to the Gulf Co-operation Council (GCC) after 3½ years of blockade by Saudi Arabia, the Emirates, Bahrain and Egypt is a major diplomatic defeat for the rulers of those countries.
Prime movers of the exclusion policy, Saudi crown prince Mohammed bin Salman and his Emirati counterpart Mohamed bin Zayed, had imposed ostracism and siege by land, sea and airspace.
They threatened to maintain the blockade until Qatar shut down its Al Jazeera satellite television channel, cracked down on the outlawed Muslim Brotherhood, cooled relations with Iran, shut down a Turkish military base and conceded another nine demands seen in Doha as infringing on Qatari sovereignty.
When Qatari emir Tamim al-Thani refused to capitulate, the demands were forgotten. He dropped lawsuits targeting the four and was invited to Tuesday’s GCC summit at al-Ula, a Saudi pre-Islamic site.
While the summit touted reconciliation, the council remains riven by division, and the instigators of the anti-Qatar policy, the two Mohammeds, have been diminished by their failure to bring Qatar to heel. Instead they have boosted Qatar’s independence by forcing it to branch out of its Gulf comfort zone.
While under siege, Qatar, a bulbous peninsula jutting out from Saudi Arabia, reduced reliance on its neighbour, developed alternative trade routes, redirected commercial air traffic over Iran on payment of $122 million a year, and strengthened ties with Turkey, a haven for Arab Brotherhood fugitives. Al Jazeera continued to broadcast unwelcome criticism of Arab rulers.
Kuwait was the main mediator in protracted talks between Qatar and Saudi Arabia that nearly resulted in bilateral reconciliation last year. The council deal was reached only when the Emirates, which is fearful of Brotherhood influence, dropped its opposition to lifting the blockade. Donald Trump's administration envoy, Jared Kushner, turned up to celebrate the deal and claim credit for its success.
Credit is due to incoming US president Joe Biden, who has pledged to reset relations with Saudi Arabia, which had been granted freedom of action by the current administration, and with Iran by returning to the 2015 deal limiting its nuclear programme in exchange for sanctions relief.
The Saudi and Emirati rulers have called on Mr Biden to consult with them before taking this step, but this is unlikely. He cannot waste time. The window is closing. Moderate Iranian president Hassan Rouhani, an author of the nuclear deal, is due to leave office after June's presidential election, and successor candidates will be chosen by hardline clerics who take orders from supreme leader Ayatollah Ali Khamenei, who initially backed the agreement.
The Gulf will benefit if Mr Biden re-enters the nuclear deal and reduces tensions with Iran by easing sanctions. Once this is achieved, the incoming US president intends to negotiate over Iran’s ballistic missile arsenal and involvement in Arab affairs, two issues uppermost in the minds of Gulf rulers.
While pressing Iran on these issues, Mr Biden and US Congress may cut the flow of American weapons to the Saudi and Emirati armies and press for an end to the deadly and destructive Yemen war and peace with the rebel Houthis.