Lilienthal was born in 1913 in New York City. He is a graduate of Cornell University and Columbia Law School. As an American of Jewish faith, he first became interested in the Middle East while in the U.S. military and stationed in Egypt during World War II. In 1949, his article, "Israel's Flag Is Not Mine," published in the Reader's Digest, caused great controversy because of its anti-Zionist position. Lilienthal has remained in the forefront of the struggle for a balanced U.S. policy not dictated by favoritism toward Israel. He continues today to call for an independent State of Palestine.