Well before the sun set on Sept. 11, 2001, defense analysts and terror experts were almost unanimous in their assessment of our nation’s future.

If was not a matter of “if” we would be hit again, but “when.”

The head of the Defense Intelligence Agency, Lt. Gen. Vincent Stewart, told the U.S. Senate Armed Services Committee, that he believes this is the year it will happen.

The Islamic State, he said, is going to continue to hit Europe and well might plan a coordinated attack on our shores.

When will it occur? The general didn’t say. He cannot know.

In reality, though, he didn’t provide a serious scoop on what’s been understood since the terror attacks of 9/11.

That attack on the World Trade Center and the Pentagon was so daring, so audacious, so brilliantly executed that it prompted President Bush and his national security team to create an entirely new Cabinet agency assigned to protect us. The Department of Homeland Security has been on the job ever since.

Now, the question always has been: Will this country be able to protect itself forever against the next terror attack? There can be zero guarantee against another attack that could rival the horror that al-Qaida brought to our shores on the beautiful Tuesday morning in New York and Washington.

But then again, had we been fully alert to the dangers that always have lurked, perhaps we shouldn’t have been so totally shocked at what transpired that day.

The Bush administration — once it gathered itself after the horror of that day — managed to keep us safe for the remainder of its time in office. The Obama administration has kept up the fight and has continued to keep the terrorists at bay.

But Gen. Stewart’s prediction of another terror attack — this time by the Islamic State — shouldn’t be seen as a big-time news flash.

Al-Qaida managed to get our guard up. Our task always has been to ensure we stay on the highest alert possible.

The enemy, though, is as cunning as they come. Many of us will not be surprised when they strike again.