On 18 May, Government of National Accord (GNA)-affiliated forces launched a surprise attack on Libyan National Army (LNA) forces based at Brak al-Shatti airbase in south-west Libya. The attack was conducted by the Misratan led-Third Force and units from the Benghazi Defence Brigades (BDB). The attack has been described as a massacre, with at least 74 LNA fighters believed dead and some reports putting the death toll at nearly 150 people. Some reports claim bodies were found with headshot wounds and tied hands, indicating they were executed in custody.The LNA accused the Third Force of breaking the implicit ‘ceasefire’ between the rival forces in south-west Libya which had been in place since LNA commander Khalifa Haftar met GNA prime minister Fayez al-Serraj in the UAE earlier this month. The LNA has also accused the attacking force of being in league with jihadists and terrorists. The GNA-aligned Misratan-led Third Force commander Jamal al-Triki admitted responsibility for the attack, saying that it was based on instructions from the GNA, but denied that any ceasefire arrangements existed between Haftar and Serraj.The Brak attack has left the GNA and its supporters in complete disarray. On 19 May, the GNA issued a statement blaming Haftar and the LNA for escalating the conflict in south-west Libya through its recent military operations in the area, thus provoking the militant reaction from the GNA-aligned forces. However, the GNA denied it had ordered the attack. On 20 May, the GNA issued a decision suspending both its Defence Minister Mahdi al-Barghathi and Jamal al-Triki, pending an investigation into the incident. Head of the High Council of State (HCS) Abdurrahman Swehli criticized the GNA for its decision to suspend Bargathi, reaffirming its demand for the removal of foreign minister Taher Siala. Siala came under fire from anti-Haftar factions within Tripoli after referring to Haftar as the legitimate commander of the Libyan Armed Forces.The Misrata Municipal Council and pro-GNA Misratan political leaders issued statements condemning the Brak atrocities but included caveats. They blamed Haftar and the LNA’s 12th Brigade, led by Mohammed Bin Nayel, for provoking the attack by conducting airstrikes and shelling against Teminhint airbase – an airbase close to Brak al-Shatti controlled by the Third Force -- for the last two months. On 21 May, a meeting was held in Misrata bringing together the (now-defunct but still socially powerful) Misrata Military Council and some military officers from the GNA-aligned al-Bunyan al-Marsus coalition which fought against ISIS in Sirte last year. They denounced statements by the GNA and pro-GNA Misratan politicians who criticized the operation, and announced they no longer recognized the authority of the GNA.The LNA responded to the attack with a series of heavy airstrikes on Third Force and Benghazi Defence Brigade (BDB) positions in the Jufra area in south-west Libya, including Hun, Sokna and Waddan. A number of fighters were reportedly killed, while some civilians were injured, amongst them some foreign workers. A meeting between various tribes in Sebha denounced the Brak al-Shatti massacre and gave the Third Force three days to withdraw from south Libya or face retaliation. The situation between various tribes in southern Libya remains highly fragile and renewed violence could lead to a dramatic escalation of conflict in the region.The events of the last two weeks show that Serraj does not have the support base necessary for a political deal with Haftar. This likely means that either Serraj will be forced to abandon political reconciliation and ally more openly with hard-liner groups such as the BDB and Misratan militias in order to counter the LNA, or he must continue trying to work with Haftar and risk losing political support for his leadership and the GNA altogether. The former approach is likely to completely derail peace talks and could result in civil war between eastern and western factions. The latter approach would likely leave the capital and the western/southern regions highly vulnerable to escalated conflict, and could result in a situation where Serraj and his allies in the GNA are evicted from Tripoli. Any peace deal made in this context would likely favour Haftar and his allies.