NEW YORK (CBSNewYork) — After a briefing at the Pentagon about U.S.-led air strikes against ISIS in Syria this weekend, President Barack Obama said the massive bombardment is the right way to defeat the terrorist group.

But it will be a long war.

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The president has been under intense pressure to wipe ISIS off the battlefield and on Monday afternoon spoke about 16 air strikes over the weekend on the Syrian city of Raqqa and the need for an international coalition to smother the terror group’s cells around the world, CBS2’s Marcia Kramer reported.

“In order for us to succeed long term in this fight against ISIL we have to develop local security forces that can sustain progress,” Obama said. “If we try to do everything ourselves all across the Middle East, all across north Africa we’ll be playing Whack-A-Mole and there will be a whole lot of unintended consequences that ultimately make us less secure.”

The Pentagon said warplanes unleashed one of their largest-ever bombardments on the city in eastern Syria, killing at least 10 militants and wounding many others.

The weekend strikes targeted bridges and transit routes in the group’s self-declared capital. It was designed to disrupt the ability of the ISIS warriors to stop Kurdish ground advances.

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“It’s very important. That’s the manner in which effective and lasting defeat of ISIL will occur, when there are effective, local forces on the ground that we can support and enable so that they can take territory, hold territory and make sure that good governance comes in behind it,” Secretary of Defense Ashton Carter said.

Also targeted was a van full of ISIS fighters. Activists claimed eight civilians standing nearby were killed.

ISIS fighters were reported to be live tweeting and they said that the city of Raqqa was shaking.

“ISIL is opportunistic and it’s nimble,” Obama said. “But today it’s also important to recognize the progress that’s been made. Our coalition has now hit ISIS with more than 5,000 air strikes. We’ve taken out thousands of fighting positons, bomb factories and training camps.”

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The president once likened ISIS to a junior varsity team, but is doing it no more. He said that in addition to military might, the coalition to fight ISIS must deal with its social media prowess and get local forces to establish government and societies attractive to the people who live there, Kramer reported.