On April 4, "the Syrian regime attacked its own people with chemical weapons," said Mattis, who added that there can be "no doubt the Syrian regime was responsible for the decision to attack and the attack itself."
Mattis explained that CENTCOM provided President Donald Trump with options for addressing the chemical weapons attack, and they "determined that a measured military response could best deter the regime from doing it again."
Sharyat air base, the location struck by 57 of 59 cruise missiles fired from the US Navy on April 7, was determined to be the location from which Syrian forces launched the chemical attack on civilians, according to Mattis.
Mattis was repeatedly questioned about the change in tactics in Syria. He maintained that the US's "military priority in Syria has not changed," and that "the Syrian regime should think long and hard" before it uses chemical weapons again.
Thomson Reuters FILE PHOTO: U.S. Navy guided-missile destroyer USS Porter (DDG 78) conducts strike operations while in the Mediterranean Sea
"The purpose of this attack was singular," said Mattis, who stressed that the US's main objective in Syria remains focused on destroying ISIS.
Mattis concluded that the strike "severely degraded" Syria's ability to launch chemical weapons attacks, though the Syrians flew out of Sharyat airbase less than 24 hours later.
Neither Mattis or Votel would comment on if Iran or Russia had knowledge of the chemical weapons use.
Votel also demurred when asked about further US deployments to Syria, which the Pentagon has elected to keep quiet.