On August 8, 2014, the U.S. launched the first airstrikes against ISIS in Iraq from the USS George H.W. Bush.

Two-and-a-half years earlier, President Barack Obama had pulled all U.S. forces out of the country, declaring the war ver. Then-Defense Secretary Leon Panetta was there as the U.S. flag lowered.

He was uncomfortable with the move then and doesn’t want to repeat the same mistake twice.

“I think the United States is going to have to have a long-term presence both in Iraq and in Afghanistan if we’re going to maintain stability there,” Panetta said.

There is debate about when to mark the start of the U.S. military’s involvement in Iraq.

The U.S. effort in Iraq dates back to 1991, the first Gulf War. The U.S. Air Force has had a near constant presence in the skies above Iraq ever since.

On March 20, 2003, President George W. Bush announced the start of the war. U.S. shock and awe began and more than 90,000 U.S. troop set off their thunder run to Baghdad.

Saddam Hussein was found, tried and later hanged. The war devolved into a civil war between Sunnis, Shias and Kurds.

President Bush ordered the surge of 30,000 U.S. forces. American troop levels rose to 166,000 at its peak.

The leader of today’s ISIS movement, Abu Bakr Al Baghdadi, had been jailed by U.S. and Iraqi forces during those surge years. He launched his self-proclaimed caliphate in Mosul on July 4, 2014 – less than three years after the U.S. troops pulled out.

“When there is an absence of forces, that provides a vacuum and others can go in there.”

Now the U.S. has deployed about 5,000 American troops on the ground in Iraq, advising Iraqi forces and calling airstrikes. Another 1,000 U.S. troops are doing the same in neighboring Syria.

Defense Secretary James Mattis said the plan is to surround ISIS.

“We carry out the annihilation campaign, so we don’t simply transplant this problem from one location to another,” Secretary Mattis said.

Nearly 4,500 U.S. troops were killed in Iraq from 2003 to 2011. More than 30,000 were wounded.

Right now, the USS George H.W. Bush – the same aircraft carrier strike group that launched the first strikes against ISIS – is poised in the Mediterranean to respond should the president order another strike, should Assad use chemical weapons again.