Here’s how Defense Secretary Mattis marked his first day back at the Pentagon

Saturday marked the first official day on the job at the Pentagon for Secretary of Defense James Mattis, and he didn't waste any time getting down to business. According to a Department of Defense press release, Mattis oversaw a total of 31 airstrikes on the Islamic State terrorist group in parts of Iraq and Syria. The Pentagon stated the operation carried out 25 strikes in Syria and six strikes in Iraq.

The Syrian airstrikes were largely successful, engaging a total of 13 ISIS tactical units, destroying ISIS positions and several vehicles along the way. In Raqqa, the Syrian ISIS headquarters, an improvise- bomb factory was destroyed along with an ISIS headquarters, two tunnels and nine fighting positions.

In Iraq, the strikes destroyed key components of the terrorist group, engaging six tactical units and hitting a command-and-control node, two weapons caches and a mortar, several vehicles, and an ISIS-held building. Near Mosul, two strikes destroyed a vehicle-borne-bomb factory, a vehicle-borne bomb, a tank, three fighting positions and a vehicle, and successfully suppressed an ISIS tactical unit.

The strikes were part of the continued efforts of Operation Inherent Resolve, an operation that the Department of Defense says seeks to "degrade and defeat the Islamic State of Iraq and the Levant, or ISIL" through targeted airstrikes.

The Defense Department indicated the strikes were effective in further hindering ISIS' presence and limited the group's "ability to project terror and conduct operations."

Mattis had criticized former President Barack Obama for his handling of the terrorist group. He told Time in August that Obama's war on ISIS was "unguided by a sustained policy or sound strategy [and was] replete with half-measures."

The retired Marine Corps general also told the Senate Armed Services committee in January 2015 that he thought the U.S. should play offense rather than defense when it came to ISIS. "[We need to] come out from our reactive crouch and take a firm, strategic stance in defense of our values," he said.