As concerns mount that Israel’s parallel war with Lebanon could jeopardize progress in U.S.-Iran negotiations, here’s what to know about the conflict, its key players, and the steeped history behind the clashes.

The announcement of a two-week ceasefire between the United States and Iran has brought mixed feelings across the Middle East, some relief, some anger and lots of uncertainty. Israel unleashed its biggest attacks in Lebanon since the war began, killing ...