Shimon was born on September 2, 1929 to Pinchas and Devora. The family made aliyah in 1935 and settled in Jerusalem. Shimon studied in the Maale School, finishing in 1947. He was in the religious division of the Scouts, in the Masuot tribe, in which he was a scout. He enlisted in Gadna, as well as some time in Hish. In summer 1947, the command staff of the Hagana gave him a secret mission: to enlist in Lehi and to report back to the Hagana. As a good and obedient soldier, Shimon did as he was told. However, he spent a great deal of time living with his fellow Lehi members and came to know them well. He was impressed by their fighting spirit, their boundless courage and motivation. He always was conscious that he was on a mission from the Hagana, but he felt like a Lehi member in his day-to-day activities and in the ongoing fighting.
As this was a transitional period, as it was the Arabs and not the British who became the enemy, things were a bit easier. Now, they were all fighting the same battle. Shimon was trained as a commander in the Lehi camp at Sheikh Badr, and he went out to fight the Arabs. This included capturing the Taunus Building, Shahin Hill and Der Yassin. Because of his pleasant voice, he became a newsreader on the Lehi radio station. His Hagana comrades recognized his voice. He enlisted in the Palmach, serving in Battalion 4, Company A (under Uri Banner). However, when he learned that Lehi was planning to break into the Old City on May 14,1948, he “deserted” his unit and joined his fellow Lehi members in this battle. The attempt was made via Jaffa Gate, but it failed; Shimon was injured by the shockwave from the blast.
In his Palmach unit, he was part of the attempt to capture Radar Hill by Nabi Samwil. Afterwards, he was transferred to field intelligence. In 1950, he underwent officers’ training.
He studied at Hebrew University, earning his BA in 1953 in economics and history. He then travelled to the United States, studying at Columbia University and earning an MA in international relations in 1955.
In 1953, he married Carmela Schechtman, and they had a son Yuval. Carmela died in a traffic accident. In 1963, he married Rosette Cohen, and they had two daughters, Lilach and Tamar; a son, Amnon; and numerous grandchildren.
Shimon worked as an economist and industrialist. In his reserve duty, he reached the rank of lieutenant colonel.