Five years ago this month, the world looked on with shock as the United States was subjected to the worst terror attack in its history. On September 11, 2001, radical Islamists hijacked four commercial airplanes and crashed them into the World Trade Center in New York City, into the Pentagon outside Washington, D.C., and into a field in rural Pennsylvania. Nearly three thousand people were killed that day; thousands more were injured; and countless others were reduced to stunned silence.