The U.S. and Iran both conducted attacks in the Strait of Hormuz on Thursday, with Iran firing missiles and drones at three U.S. naval vessels and the U.S. striking a range of Iranian targets.Why it matters: A U.S. official told Axios the exchange did not constitute a resumption of the war, but the Iranian military described the U.S. strikes as a ceasefire violation and threatened retaliation.Driving the news: CENTCOM said it struck Iranian launch sites, command centers and intelligence nodes in response to "unprovoked" Iranian attacks on three U.S. destroyers. It said those Iranian launches were intercepted with no damage to U.S. assets. The extent of the damage inflicted in the U.S. strikes is unclear at this time. Iran's military said the U.S. had targeted an oil tanker and another ship entering the strait. The U.S. is enforcing a blockade on Iranian vessels.President Trump pulled back on his operation for the Navy to facilitate shipping through the strait on Tuesday but left the blockade in place.Catch up quick: Iran responded to the since-abandoned U.S. operation on Monday by firing on U.S. naval vessels, commercial ships, and the United Arab Emirates.Trump's pullback came as the U.S. and Iran negotiate on a one-page memo to end hostilities and lay the groundwork for more detailed negotiations.What they're saying: CENTCOM said it "does not seek escalation but remains positioned and ready to protect American forces.""Iran will respond powerfully and without the slightest hesitation to any attack," Iran's military command said.This is a breaking news story and will be updated.