For the past two years, Lebanon has tried to avoid getting drawn into the Syrian conflict on its borders. But last month Hezbollah, the country’s largest political party, admitted sending thousands of guerrillas to fight on behalf of the Syrian regime. In return, Syrian rebels and their supporters have vowed revenge - inside Lebanon itself - and sectarian tensions are escalating across the country. In this documentary, BBC Arabic reporter Nahed Abouzeid investigates a Lebanon teetering on the brink of an intra-religious war. For Our World: Lebanon On The Brink, Nahed, who was born and grew up in Lebanon, explores why, after successfully rebuilding itself following a vicious civil war, his country is on the edge again, this time of someone else’s fight. For the half hour film, Nahed talks to those caught up in the violence as well as gaining unique access to a fighter from the Lebanese Shia Muslim organization Hezbollah. Located between Syria and Israel, Lebanon has frequently been caught up in the politics and violence of its more powerful neighbours. This time, Lebanon faces sectarian violence between Sunni Muslims – who mainly support the Syrian rebels – and Shia Muslims, who mostly back the Syrian government in the capital Damascus. From Al-Qusayr in western Syria, Nahed Abouzeid tells the story of a shattered and abandoned city which was a rebel stronghold, attracting anti-Assad Islamic militants from across the Muslim world. Supported by Hezbollah, the Syrian regime launched an attack in June this year and regained control over Qusayr from the rebels. The undisguised intervention of Hezbollah’s Shia Muslim fighters has caused a sectarian backlash back across the border in Lebanon. Syrian refugees from Qusayr fled for their lives and now live in squalor just inside Lebanon’s northern border.