The rise of the Houthis in Yemen in 2014 led to the creation of a number of cross-factional alliances to counter the Iran-backed rebels. One of them, the Southern Transitional Council (STC), became part of the internationally recognised government seeking to regain control over the whole country.
But the STC itself comprises groups that seek to re-establish the separate southern state that existed before unification with northern Yemen in 1990.
What is the STC?
Southern forces trained by the UAE played a decisive role in preventing the Houthis from extending their control into Yemen's south between 2015 and 2018. This enabled the government, which fled the capital, Sanaa, in 2015, to establish itself in Aden with support from the Saudi-led coalition fighting the Houthis.
The STC, formed in 2017 and headed by Aidarous Al Zubaidi, emerged as the political umbrella for many of these forces. Its origins lie in the Southern Movement, whose aim was to "liberate" major provinces from the forces that defeated southern separatists in the 1994 civil war. The Southern Movement's senior members hailed mainly from the southern province of Al Dhale, where Mr Al Zubaidi is from.
At present, the STC is made up of 26 members who represent armed factions including the Security Belt Forces (SBF) under Muhsin Al Wali's command and the Hadhrami Elite Forces led by Faiz Mansour Al Tamimi.
What do they control?
The STC has been fighting other groups in the anti-Houthi camp to make territorial gains for years; most notably when it seized control of most of Aden in 2018. Tensions eased with the government after a Saudi-brokered agreement was struck a year later, and the STC was finally considered a part of the government.
Mr Al Zubaidi rose further in the government when he was appointed vice president of the eight-member Presidential Leadership Council (PLC) that was formed in 2022. The STC was allotted three of the PLC's seats.
Tensions escalated again last month after the STC took control of the governorates of Hadhramaut and Al Mahra from other pro-government forces − effectively consolidating its grip over much of southern Yemen.
Rival factions allied to the government, backed by air strikes from the Saudi-led coalition, have taken back the two strategic governorates, including the port city of Al Mukalla in Hadhramaut, over the past week.
Mr Al Zubaidi's whereabouts remain unclear after he failed to join other STC officials on a flight to Saudi Arabia on Tuesday for talks to resolve the situation.
The head of the PLC, Rashad Al Alimi, on Wednesday accused the STC leader of treason and revoked his membership of the council.
Videos circulating on Yemeni and Saudi media showed the Giants Brigades forces led by Abdulrahman "Abu Zaraa" Al Mahrami patrolling the streets of Aden.
Mr Al Mahrami, who is a member of the PLC, is among the STC leaders who did travel to Riyadh on Tuesday.
