Mordehai joined the movement at a very young age and was active in its local ken. He studied dentistry. For a while he joined the outlawed Socialist and Communist parties. In 1941 he enlisted in the Hungarian army from which, due to his Jewish origin, he was transferred to a labor unit. In 1944 he deserted, arrived in Budapest and stayed at the “Glass House” on Vadász and Wekerle Streets. Mordehai underwent weapons training and escorted food deliveries to children’s homes around the city. After the liberation he was a member of the hahshara in Kibbutz Ehad BeMay.
In 1946 he made aliya and settled in Kibbutz Ma’anit. He later became a member of Kibbutz Yasur and served in the IDF. Mordehai took part in the Acco and Negba battles. In the battle for Negba he volunteered to rescue wounded soldiers who were trapped in a minefield, and was killed when he stepped on a mine. He was buried in the Kibbutz Negba mass grave.