On Sept. 11, 2001, 19 people hijacked four U.S. commercial airliners after those airliners took off from airports inside the United States. They then flew those airliners into the World Trade Center towers, the Pentagon and a field outside Shanksville, Pa.
The hijackers had certain characteristics in common. All were young males from regions of the world that in recent decades had produced radicalized Muslims -- and the U.S. government had given all of them visas to enter the United States.
The oldest of the hijackers was 33; the youngest was 20; their average age was about 24. One came from Egypt, one from Lebanon, two from the United Arab Emirates, and 15 from Saudi Arabia.
The staff of the National Commission on Terrorist Attacks Upon the United States -- the 9/11 commission -- would later publish a report on how these young radical Muslim men were allowed to enter the United States and travel around our country as they prepared to murder thousands of Americans in the name of jihad.
The report said: "The relative ease with which the hijackers obtained visas and entered the United States underscores the importance of travel to their terrorist operations."
"Once the operation was underway, the conspirators attempted to enter the United States 34 times over 21 months, through nine airports," said the report. "They succeeded all but once."
"Every hijacker submitted a visa application falsely stating that he was not seeking to enter the United States to engage in terrorism," said the report. "This was a felony, punishable under 18 U.S.C. Section 1546 by 25 years in prison and under 18 U.S.C. Section 1001 by 5 years in prison, and was a violation of immigration law rendering each one inadmissible under 8 U.S.C. Section 1182(a)(6)(c)."
What strategy did the United States pursue to protect the liberty and security of Americans from future attacks like the ones carried out inside the United States by these 19 young radicalized Muslim males from Egypt, Lebanon, the United Arab Emirates and Saudi Arabia?
It encompassed many things, including, we now know, activities as far-flung as supporting revolutions in Middle Eastern countries and tapping directly into the servers of Internet companies like Google and Facebook. But it did not include stopping Umar Farouk Abdulmutallab, a 23-year-old radicalized Muslim male from Nigeria, from boarding Detroit-bound Northwest Airlines Flight 253 in Amsterdam at Christmas 2009.
Had Abdulmutallab's underwear bomb worked, Flight 253 would have been blown out of the sky.