Loy W. Henderson, 93, one of this country's most respected diplomats, an authority on the Middle East and a special U.S. envoy in a variety of troublesome and volatile situations in the years after World War II, died of congestive heart failure March 24 at Carriage Hill Nursing Home in Bethesda.

Mr. Henderson played an important and controversial role in setting the State Department's policy toward establishment of the State of Israel in 1948. He was instrumental in helping stop an attempted communist takeover in Greece in the years immediately after the war and formulating what became known as the Truman Doctrine.

In the early 1950s he was ambassador to Iran at a time when the shah was briefly deposed and the Anglo-Iranian Oil Co. was nationalized. Through these and other policies of prime minister Mohammad Mossaddeq, the country was brought to the edge of bankruptcy. With the intervention of the Central Intelligence Agency, the crisis ended with a military coup and the arrest and imprisonment of Mossaddeq.

During the 1956 crisis over the nationalization of the Suez Canal by President Gamal Abdul Nasser of Egypt, Mr. Henderson was a special representative of President Eisenhower and Secretary of State John Foster Dulles at high-level meetings in Europe.

As an administrator, he played an important role in implementing a critical and sensitive reorganization of the Foreign Service. This was the plan proposed by Henry M. Wriston, president emeritus of Brown University, and it remains today as the basis of the country's professional diplomatic corps.

Mr. Henderson was a Foreign Service officer for 39 years before retiring in 1961. His assignments included a tour as minister to Iraq in World War II and, in 1933, he was one of the leaders of the team that established the U.S. diplomatic mission in Moscow after President Roosevelt's recognition of the Soviet Union.

From his experience in Russia in the 1930s he was convinced that the U.S. relationship to the Soviets in World War II should be one of cobelligerency, not of alliance, and he remained a forceful opponent of communist expansion throughout the remainder of his career.

Among the numerous honors Mr. Henderson received was his inclusion among the select group of Foreign Service officers who received the personal rank of career ambassador when that grade was established in 1956. He also held the President's Award for Distinguished Federal Civilian Service and the State Department's Distinguished Service Award. He received personal commendations from presidents Roosevelt, Truman and Eisenhower. A State Department newsletter in November 1967 said he held the "undisputed title of 'Mr. Foreign Service.' "

Secretary of State George P. Shultz said yesterday that Mr. Henderson was a "most distinguished diplomat . . . known for his leadership and high sense of integrity."

The son of a Methodist clergyman, Mr. Henderson was born in the Ozark Mountains near Rogers, Ark., and as his father's pastorates changed he was reared in Arkansas, Ohio, Kansas and Utah. He graduated from Northwestern University and attended law school at the University of Denver.

Unable to serve in the military during World War I because of a childhood arm injury, he left law school and joined the American Red Cross in France. After the war he served in the Red Cross in Russia, the Baltic States and Germany before passing the U.S. consular examinations in 1922.

His first post as chief of a U.S. diplomatic mission was as minister to Baghdad in the last years of World War II. He then returned to Washington as head of the State Department's Office of Near Eastern, South Asian and African Affairs. It was in that capacity that he became the author of the recommendations of U.S. aid to Greece and Turkey that became the Truman Doctrine.

And it was in this post that he opposed the partition of Palestine and the creation of the State of Israel, which resulted in charges that he was pro-Arab. While Mr. Henderson did not respond personally to that criticism, his supporters at State said he was simply trying to keep U.S. policy in balance in the face of excessive support for the new Jewish state.

Mr. Henderson was named ambassador to India in 1948. Two years later he persuaded Prime Minister Jawaharlal Nehru to support the United Nations' intervention in the Korean War. In 1951, Mr. Henderson began his assignment as ambassador to Iran.

His return to Washington in 1954 as deputy under secretary of state for administration coincided with the preparation and implementation of the "Wriston Report" at the behest of Secretary of State John Foster Dulles. The report called for the merging into one organization of the Civil Service and Foreign Service officials of the State Department.

It was sometimes called a "shotgun marriage" between a corps of civil servants who were never required to serve overseas and Foreign Service personnel who rarely served at home. There was opposition to the proposal on both sides. It was carried out successfully, however, and Mr. Hendeson received much credit for the tact and understanding with which he supervised it.

In retirement, Mr. Henderson served for seven years as professor at the School of International Service at American University. He was a founder and former president of the Washington Institute of Foreign Affairs and a former president of DACOR (Diplomatic and Consular Officers, Retired).

Survivors include his wife of 56 years, the former Elise Marie Heinrichson, of Washington.