Brief History.

The article offers a brief history of double agents beginning with Jordanian physician Humam Khalil Abu-Mulal al-Balawi's December 30, 2009 suicide bombing of a U.S. Central Intelligence Agency base in Afghanistan that killed seven employees. The use of double agents in the fourth century B.C. book "The Art of War" by military strategist Sun Tzu is explored. The double agents in U.S. intelligence agencies including senior U.S. Federal Bureau of Information agent Robert Hanssen are discussed.