Israel and Iran traded fire on Monday, all but derailing a brittle two-month ceasefire that had largely stopped the fighting.

Iran’s attack on Israel threatens to escalate a conflict that has been largely contained since a ceasefire in April, as the president urges all sides to pull back.

Monday’s strikes by both Iran and Israel are the most serious escalation in the conflict since the ceasefire between the U.S.-Israel side and Iran went into effect in April.