Sagi entered the Israeli Defense Forces in 1951. From 1953 to 1954, he served in the
Southern Command, fulfilling field duties. During the
Suez Crisis in 1956, he served as intelligence officer of the Armored Corps and as commander of a reconnaissance unit. Following the 1956 war, he served as an intelligence officer with the 7th Brigade, and later as assistant intelligence officer. From 1967 until 1970, he was an intelligence officer in the Southern Command, and during the
Yom Kippur War was a divisional intelligence officer. In 1974 he became assistant to the head of research at the Military Intelligence Directorate. After serving as deputy head beginning in 1978, he rose to become head of Military Intelligence in 1979. Sagi opposed
Operation Opera, the 1981 Israeli attack on the Iraqi Osirak nuclear reactor, saying "I do not believe fears of a 'Second Holocaust' justify the Israeli military taking any steps it thinks fit". During the leadup to the
1982 Lebanon War, Sagi was charged by Prime Minister
Menachem Begin with obtaining some form of American approval for an Israeli ground invasion of Lebanon. The result was the admission by U.S. Secretary of State
Alexander Haig that the infiltration of terrorists over any of Israel's borders constituted a violation of the July 1981 ceasefire, but not terrorist actions against Israeli or Jewish targets outside of the region. Sagi was asked to resign in 1983 following the recommendations of the
Kahan Commission, which had determined that he was guilty of indifference during
massacres at
Palestinian refugee camps in Israeli-occupied
Lebanon. Sagi subsequently resigned from the army. ==Political career==