Cleveland - Sen. Johnny Isakson delivered a full-throated endorsement of Donald Trump on Monday, telling Georgia delegates to Cleveland's convention they needed to sign up as a "volunteer for the Army of America" to elect the presumptive Republican nominee.

And he criticized President Barack Obama’s administration for waging what he described as a halfhearted war on the Islamic State, arguing that the attacks in Orlando, California and elsewhere by gunmen inspired by the terror group marked a point of no return.

"What we tolerate, our kids will embrace," he said Monday, as Georgia's 76 delegates and 73 alternates prepared for the first day of the four-day convention.

“They want us to cower in fear. If we do that, they’ve won. The media asks me what am I going to do to stop the violence on the streets. My answer is whatever it takes,” he said. “There is no second-guessing. We’ve got to do it. If we don’t, America’s gone. There is no coming back.”

In an interview, Isakson elaborated on his definition of "whatever it takes."

"It means that in terms of confronting ISIL and containment like we have today is just not enough," he said, using an acronym of the Islamic State. "There are places where we can deploy the right type of ground forces, like special operations forces. Not an invasion force, not a surge like we had in Iraq. With 13 people we took out Osama bin Laden once we found out where he was. We know where a lot of these ISIL leaders are. It should be untenable for them to continue to exist."

Isakson, who is running for re-election against Democrat Jim Barksdale and Libertarian Allen Buckley, was then asked if the nomination of Trump this week would mark the "last vestiges" of the internal GOP movement to halt his nomination.

“I haven’t seen the first vestiges of it, so I don’t know where the last vestiges are. But I believe everyone is coming together," he said. "I’ve been in this game a long time. I’ve seen a lot of disunity. But I’ve never seen this country in as much dismay since 1980 … Ronald Reagan changed that, and we need the same type of change this year before it’s too late.”

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Starting in Iowa and New Hampshire, The Atlanta Journal-Constitution has brought you every key moment in the 2016 presidential race, and our in-depth coverage will continue at the political conventions. Our team of seasoned political reporters will be on the ground in Cleveland and Philadelphia to bring you every development from these pivotal campaign events. An expanded editorial team in the Atlanta newsroom will round out coverage of both conventions.