As he pushes a cart full of tomatoes and cucumbers in the market at Bint Jbeil in southern Leba**n, **thing marks out Mahmud as an experienced Hezbollah fighter. The stocky vegetable vendor in his fifties, who sports a red beard, fought Israel here in 2006, but that battle is **w old news. He has just come back from a**ther front: in Syria, where he fought for 25 days against the rebels who have sought to overthrow President Bashar al-Assad for the past three years. Since the Shiite movement's chief Hassan Nasrallah gave the order more than a year ago, thousands of Hezbollah fighters have fought in Syria, playing a decisive role in key victories for the regime.