In a break from his predecessor, President Donald Trump quickly authorized strikes against the Syrian government —a first for the US. According to Mattis, it was meant to deter future chemical weapons use, while showing the world that the US would "not passively stand by" when such atrocities are carried out.

no doubtautopsies have showed that sarin gas was used. The Syrian government and Russia, its ally, have vigorously denied responsibility.

Russia said that instead, the Syrian air force perhaps carried out a conventional attack that hit a chemical weapons cache controlled by the rebels. However, as chemical weapons expert Dan Kaszeta explained to Bellingcat, sarin in storage consists of unmixed components, and dropping a bomb on them would not turn them into a nerve agent.

"It is an infantile argument," he wrote.

Meanwhile, Mattis' statement revealed some details of a damage assessment at the air field. It said the Tomahawk strikes destroyed or damaged fuel and ammunition sites, air defenses, and 20% of Syria's operational aircraft.

"The Syrian government would be ill-advised ever again to use chemical weapons," Mattis concluded.