Hundreds of civilians, mostly in Iran, have been killed by dueling airstrikes despite international pleas for de-escalation.

President Trump rejected an Israeli plan in recent days to kill Iran's Supreme Leader Ayatollah Ali Khamenei, a senior U.S. official told USA TODAY.

The war between Israel and Iran is in its fourth day, with Israel striking at military sites and Iran's nuclear program and Iran firing missiles in retaliation

The president had opposed Israeli action against Iran but came to believe that Israel had reason to act and that the U.S. would have to lend some support.

Emergency services reported at least three people were killed and dozens more wounded in Israel as the fourth day of open warfare between the regional foes causes air raid sirens to be triggered

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.