More than eight months into the Gaza war, Israel is threatening an all-out war against Lebanon’s Hezbollah. A recent intensification of Israeli strikes against Hezbollah commanders and operatives, supply routes, and weapons storage sites in Syria suggests that an Israeli invasion of southern Lebanon may soon begin.

Such a scenario could send dangerous shockwaves across the Middle East and beyond with various groups within the Iran-led ‘Axis of Resistance’ entering the conflict on Hezbollah’s side. Although they do not share borders with either Israel or Lebanon, the Gulf Cooperation Council (GCC) member states would have...