"We've been sleeping on the ground for two days, but we can' sleep at all. How can we sleep on gravel, with the bitter cold at night and the scorching heat during the day?" laments a Syrian refugee who fled Israeli bombardment of Lebanon, after a long four-day journey to the rebel-held areas of northern Syria. Lebanon became home to hundreds of thousands of Syrians after the repression of anti-government protests in 2011 sparked a war that has since killed more than half a million people. But heavy Israeli air strikes on Lebanon have prompted more than 400,000 people, most of them returning Syrian refugees, to cross into Syria over the past two weeks. IMAGES AND SOUNDBITES