A lot has happened since Gulf Arab states downgraded ties with Iran in January 2016 when an angry mob stormed the Saudi embassy in Tehran and set fire to it following the Saudi execution of a prominent Shiite cleric.
Iran's nuclear agreement with world powers came into effect that month, but the Trump administration withdrew from it just two years later, leading to a wave of tit-for-tat attacks that affected oil and shipping in the Persian Gulf.
Those tensions culminated in a 2019 assault on Saudi oil facilities that knocked off half of the kingdom's crude production and threatened the very core of Gulf states' economies. It was part of a proxy conflict between the US and Iran, with the Arab states caught in the line of fire.
As tensions grew, Gulf states found the US standing on the sidelines, either unwilling or unable to come to their rescue, with their own lines of communication with Iran all but severed.
But much has changed since then. The United Arab Emirates is set to restore top level diplomatic relations, saying on Sunday that its ambassador, Saif Mohammed Al Zaabi, would return to Tehran "in [the] coming days." Kuwait returned its ambassador last week and Saudi Arabia, whose lead the Gulf states followed in downgrading ties with Iran six years ago, is holding direct talks with the Islamic Republic.
"It's obvious there is a regional direction that is in tandem with Saudi movement," Mohammed Baharoon, director general of the Dubai Public Policy Research Centre, told CNN.
The decision to return the ambassador "comes within the UAE's regional orientation towards restoring bridges, strengthening relations, maximizing on what we share and building on it to create an atmosphere of trust, understanding and cooperation," tweeted Anwar Gargash, adviser to the UAE president.
Dina Esfandiary, a Middle East adviser at the International Crisis Group think tank, said Gulf Arab states have developed a "pragmatic policy" on Iran that involves both containment and engagement "because they realized just one would not work on its own."
She told CNN that, when the US didn't follow through on defending its Arab partners following the Aramco attacks "it became imperative [for the UAE] to secure itself without relying on others -- the US in particular -- and engaging with Iran is a part of that."
Ties between Abu Dhabi and Tehran have been progressively improving since then. The UAE is now the top exporter to Iran with bilateral trade rising to $21.4 billion in four months from March this year, from just $7 billion for all of 2019, according to Reuters.
"Financially and commercially, the UAE benefits the most from lessening regional tensions," Abdulkhaleq Abdulla, a political science professor in the UAE, told CNN. "Even during the worst of political tensions between the two countries, trade was uninterrupted. It went down, but never stopped."