It was 17 years ago on a beautiful Tuesday morning like today that terrorists struck America in New York and Washington.
At the Pentagon and the site of the World Trade Center, victims gathered to remember the lost. President Trump is attending a memorial service in Shanksville, Pennsylvania for the victims of Flight 93.
The 9/11 attack kicked off a war that we're still fighting today, and experts say the global threat posed by radical Islam is greater than ever.
Since that fateful September morning, Islamic jihadists have launched 33,767 deadly terror attacks.
Cliff May, president of the Foundation for the Defense of Democracies, tells CBN News, "The movements and ideologies that drove and justified that attack and the thousands of other attacks you name, that still remains very dynamic, very vibrant - a major force in the world."
And these terror groups have hit targets nearly everywhere around the world since 9/11. From Iraq and Afghanistan to Finland and California, experts say Islamic fighters have shown that they are far from exhausted, discouraged or underfunded.
"Our jihadist enemies, Sunni or Shia, they still seem very prepared to fight, not ready to put down their weapons, not ready for a diplomatic process or a peace process," May said.
ISIS, the offshoot of Al Qaeda that was born in the desert sands of Iraq and Syria, is much weaker than it once was but is by no means out of the fight.
The group has carried out more than 150 attacks in 29 countries, killing thousands.
Its affiliates or supporters are now spread around the world, including here in the homeland where the FBI's director told congressional officials this summer that his bureau was tracking an alarming number of cases.
FBI Director Christopher Wray testified, "We have about a thousand investigations into exactly the kind of people you are describing, covering all 50 states as I'm sitting here right now."
And let's not forget Al Qaeda. Even though the group has been unsuccessful in launching another spectacular 9/11-style attack, it is still alive.
Despite the death of its leader Osama Bin Laden in May 2011, Al Qaeda, which had just a few hundred fighters on 9/11, now has between 10,000 and 20,000 battle-hardened fighters in Syria. About 4,000 are operating in Libya and another 9,000 are in Somalia. Hundreds more are scattered across North Africa and Southeast Asia.
And according to Western intelligence, there are about 50,000 jihadists living in Europe, including recent combatants who have returned home from fighting alongside ISIS, Al Qaeda and other terror groups in Syria and Iraq.
"And, let's be honest about this: they are faith driven. They have an ideology that is derived from a theology," May explained.
Seventeen years later, despite trillions of dollars spent and countless lives lost, the threat from radical Islam is more widespread than ever before.
May says the world ought to prepare for a long war against an enemy that isn't backing down.
"We should look back in history and recall that we've had wars, such as in the Arabian Peninsula between Christians and Muslims that lasted close to 800 years, other wars lasted 700 years, 200 years. We don't know how long this war is going to last, our enemies don't care how long it's going to last. If we are not prepared for such a war then we will for sure lose such a war."