What is Hezbollah, the Iranian-backed group that could go to all-out war against Israel?

BEIRUT — After more than eight months of low-scale conflict, Israel and the Lebanese militant group Hezbollah are threatening all-out war. The United States and the international community are lobbying for calm and hopeful for a diplomatic solution. They have not been successful so far and time for a political settlement could be expiring. Should war break out, Israel would face a much more formidable foe in Lebanon than it faced in Hamas in the Gaza Strip. Hezbollah leader Hassan Nasrallah...