A ceasefire deal to end the fighting between Israel and Hezbollah has come into effect after Beirut residents endured the most intense day of Israeli strikes since the war began. At least 42 people were killed by Israeli strikes across Lebanon on Tuesday, according to local authorities. This morning, cars crowded the main roads as thousands of displaced Lebanese started to return south. Some people were celebrating the end of hostilities, at least for the moment. Under the truce agreement, Israeli and Hezbollah troops are to gradually withdraw from southern Lebanon, to be replaced by the Lebanese army, which says it is already "taking the necessary measures" to move in. Northern Israeli residents are also returning to their homes. What are the main obstacles for this agreement to hold? If it eventually works, could this ceasefire become a model for a similar agreement in Gaza?