The world grappled Sunday with the enormous implications after the United States inserted itself into Israel's war against Iran with an attack that raised urgent questions about what remained of Tehran’s nuclear program and how its weakened military might respond.

Prior to the attack, Iran had threatened to retaliate against the U.S. if it became involved in its conflict with Israel.

The US hit three nuclear sites in Iran overnight - but it remains unclear whether the strikes did destroy all of Iran's nuclear capabilities.