Avidan was born in 1926 in Afghanistan, to Avraham and Hannah Mashiach. His father was a merchant, and in 1934 he arrived in the Land of Israel “to survey it” and make preparations for his family’s aliyah. A year later, the family made aliyah and settled in Jerusalem. In addition to the three children born in Afghanistan, three were born in the Land of Israel. Out of the six, three served in IZL and Lehi.

Avidan grew up in the northern neighborhoods of Jerusalem, from which many joined the underground to fight the British. After completing eighth grade in the Alliance School, he continued to study for matriculation exams, taking odd jobs in the meantime to support the family. He joined Brit Hashmona’im. In 1945, he joined Lehi.

At first, he would disseminate promotional material by day and put posters by night, dangerous activity. Ultimately, it was only his deep knowledge of Jerusalem’s backstreets and courtyards that allowed him to escape arrest — or even being shot! Later, he took a course with Yaakov “Blond Dov” Granek in light arms, and he started participating in combat operations. He gathered intelligence, but he also worked on the medical front, recruiting doctors and nurses, acquiring medicines and equipment and building a medical infrastructure. He also recruited supporters and fundraised. More than once, these activities almost got him arrested or shot, as he was more than once in situations in which he had no way to escape and just a weapon in his hand. In these instances, his calm and cool demeanor saved him. His knowledge of French made him a candidate to travel there and join the cell operating in Europe, but the arrest of activists in France led to the cancellation of his trip. During the War of Independence, he fought in Lehi units in Jerusalem.

After Lehi was disbanded, he joined the IDF, but he was released soon after due to illness. He pursued Jewish studies, literature, Bible and language at Hebrew University. From 1953 to 1967, he was the parliamentary correspondent and night editor of Herut. He was also a journalism teacher at the British Institutes. In 1967, he worked at the Jerusalem Municipality as director of the publications department. He was the editor of the Sephardic Community Council of Jerusalem magazine and also edited books. In 1983, he took early retirement from the Jerusalem Municipality and went to direct public relations and publications for Misgav Ladakh Hospital until he retired.

In 1959, he married Naomi Yona-Golomb, a teacher. They live in Jerusalem and have four children and numerous grandchildren.