Several buildings in Israel’s Weizmann Institute of Science, one of the country’s top research centers, were damaged in an Iranian strike but there were no casualties, its management told its community members.

Iran has vowed to retaliate against the U.S., too, while Trump has warned: “If we are attacked in any way, shape, or form by Iran, the full strength and might of the U.S. Armed Forces will come down on you at levels never seen before.” Here’s what to know about U.S. involvement so far.