Forces loyal to the Saudi-backed Hadi government in Yemen have been chased out of the their own self-declared capital city of Aden by UAE-backed separatist rebels after the latter's launching of a blitz offensive.
Technically, both pro-Hadi forces and Southern Resistance (STC) rebels always had military units inside the city and shared control peacefully under a ceasefire agreement that was enacted after hostilities between the two sides earlier in 2018.
Both groups have often participated in joint operations against the Houthi (Ansar Allah) movement across western Yemen throughout most of the war so far.
However, in recent days a blitz offensive by Southern Resistance forces in Aden managed to completely overwhelm pro-Hadi loyalists, with STC units securing the presidential palace and the main military barracks of the city; the UN reports that as many as 40 people have been killed as a result of the fighting.
Aden is one of Yemen's largest port cities and its capture by STC separatists may very well serve to change the balance of power in Yemen on the ground between all the warring factions.
Saudi Arabia's designation of the STC as a terrorist group amid the reported withdrawal of UAE involvement in the Yemen conflict appears to have been inappropriate timing that may very well have spurred-on the separatist rebels to launch an attack on pro-Hadi forces and secure a highly-strategic location.