Yemen has been at war since Iran-backed Houthi rebels ousted the government in 2014, triggering a Saudi-led military intervention, but a new internal conflict has been brewing in recent weeks.The face-off involves rival armed factions loosely grouped under the government but separately backed by the United Arab Emirates and Saudi Arabia.The UAE on Tuesday said it was pulling its remaining forces out of Yemen, following a Saudi demand to withdraw within 24 hours as tensions escalate over a sweeping offensive by Abu Dhabi-backed separatists, who have refused to pull back.Here is what we know about the latest events threatening the already-fractured government and what could happen next.- What’s happening now? -This month, the Southern Transitional Council (STC), a UAE-backed secessionist group and key government partner, seized most of resource-rich Hadramawt province and swaths of neighbouring Mahrah. Saudi Arabia, chief supporter of Yemen’s government, has hit back, and tensions escalated Tuesday when a Saudi-led military coalition attacked an alleged shipment of weapons and combat vehicles it said was sent from the UAE to the separatists.The UAE denied sending weapons to the STC.After the strikes, Yemen’s presidential council dissolved a defence pact with the UAE and declared a 90-day state of emergency.The strikes came after raids hit STC positions on Friday, following calls from Riyadh for a separatist withdrawal. Later Tuesday, the UAE announced its remaining forces would leave Yemen, before an STC spokesman vowed the separatists would hold their positions.A Yemeni military official said around 15,000 Saudi-backed fighters were massed near the Saudi border, with no orders to advance.”The standoff risks upending Yemen’s fragile three-and-a-half-year truce,” wrote April Longley Alley, a senior fellow at the Washington Institute, in an analysis.”It could also further strain relations between key US allies Saudi Arabia and the UAE.”- What does the STC want? -The STC appears to be launching a bid for greater self-determination over territories it controls or even outright independence, observers said. Headed by Aidaros Alzubidi, the STC is a coalition of groups that want to bring back South Yemen, which existed from 1967 to 1990, when it reunified with North Yemen.They now control almost all of South Yemen’s former territory.The STC “is betting that if the South can be united under a single leadership –- its own, of course –- it can cordon the South off from the Houthis in the North, utilise oil and gas revenue, and create a stable and functioning state,” wrote Gregory D. Johnsen, a non-resident fellow at the Arab Gulf States Institute, in a recent analysis.Such a move “is a tall order, and it will likely be contested both internally and externally”, Johnsen added.- Why is Saudi ‘sleepless’ over Hadramawt? -Hadramawt is Yemen’s largest province, comprising roughly a third of the country’s territory, and its wealthiest.It is home to most of Yemen’s vital petroleum deposits, and its ports are away from the Red Sea hotspot that regularly comes under Houthi fire.But for the Saudis, the province abutting their southern border is about more than just land and wealth. For generations, Hadramawt families have been a force in the Saudi economy and make up a sizeable portion of the business community.Seen as having entrepreneurial skills and grit, migrants from Hadramawt have long flourished in Saudi Arabia, from running family restaurants to starting multi-billion dollar construction consortiums. Losing Hadramawt to a UAE-backed militia would be a strategic blow to Riyadh.”If I’m Saudi Arabia, I’d be sleepless if I lose Hadramawt,” said Farea al-Muslimi, a research fellow at Chatham House’s Middle East and North Africa Programme. – Can the Saudis stop the separatists? -The latest escalation pits the Saudi alliance against a militia keen to exert control over territory it sees as historically distinct from the rest of Yemen. The decade-long, largely fruitless fight against the Houthis may not give Riyadh much cause for optimism. Despite spending billions in a campaign including air strikes, the Saudi-led intervention has failed to bring the Houthis to heel.Military experts cite the south’s more open terrain as playing to Saudi Arabia’s possible advantage. An air campaign alone, however, is unlikely to dislodge their forces. Air strikes “can never make a significant difference in battles if there is no ground war”, said Muslimi.