The US military has carried out a “massive strike” against Islamic State (IS) in Syria following a deadly attack on American forces. Defence Secretary Pete Hegseth said Operation Hawkeye Strike aimed to destroy IS fighters, infrastructure, and weapons sites. Fighter jets, attack helicopters, and artillery hit multiple targets in central Syria. Aircraft from Jordan also joined the strike. President Donald Trump said, “We are striking very strongly” against IS after the 13 December ambush in Palmyra. Two US soldiers and a US civilian interpreter were killed in that attack. On X, Hegseth declared, “This is not the beginning of a war - it is a declaration of vengeance.” He warned, "If you target Americans - anywhere in the world - you will spend the rest of your brief, anxious life knowing the United States will hunt you, find you, and ruthlessly kill you." He added, “Today, we hunted and we killed our enemies. Lots of them. And we will continue.” US Central Command (Centcom) confirmed a large-scale strike against IS had begun and promised more details soon. President Trump wrote on Truth Social that the US “is inflicting very serious retaliation, just as I promised, on the murderous terrorists responsible,” and said the Syrian government was “fully in support.” The UK-based Syrian Observatory for Human Rights (SOHR) reported IS positions near Raqqa and Deir ez Zor were hit. It said a key IS leader and several fighters were killed. IS has not yet responded. Centcom reported the deadly Palmyra attack was done by an IS gunman who was “engaged and killed.” Three other US soldiers were injured. The attack took place in an area outside Syrian President Assad’s control. Meanwhile, SOHR claimed the attacker was a Syrian security force member. No group has claimed responsibility, and the gunman’s identity is unknown. In 2019, a US-backed Syrian alliance declared IS had lost its last territory in Syria, but the group still carries out attacks. The United Nations estimates IS still has 5,000 to 7,000 fighters in Syria and Iraq. US forces have been in Syria since 2015 to train local troops in the fight against IS.