WASHINGTON (AP) — The United States launched a new barrage of airstrikes Wednesday against the Islamic State extremist group that beheaded American journalist James Foley and that has seized a swath of territory across Iraq and Syria. President Barack Obama vowed relentless pursuit of the terrorists and the White House revealed that the U.S. had launched a secret rescue mission inside Syria earlier this summer that failed to rescue Foley and other Americans still being held hostage.

In brief but forceful remarks, Obama said the U.S. would “do what we must to protect our people,” but he stopped short of promising to follow the Islamic State in its safe haven within Syria, where officials said Foley had been killed. Later, though, the administration revealed that several dozen special operations troops had been on the ground in Syria briefly in an effort to rescue the hostages, but did not find them.