Mordechai Nissim was born in Jerusalem on December 1927 to Eliyahu and Sarah. He studied in high school and also acquired a religious education. He was a member of ‘Hashomer-Hatsa’ir’ and after studying at the ‘Histadrut Workers Seminary’ obtained clerical work. When the riots broke out he began escorting convoys. His revolutionary aspiration could not support the leadership’s passive inaction in the face of events, particularly in Jerusalem.

He therefore joined Lehi, finding great support among the fighters because of his love for the homeland. His letters home reveal great dedication to his parents.  After the British left Jerusalem,  Friday May 14, 1948, Lehi stormed the abandoned city quarters taking over, amongst others, the Barclays Bank building, ‘Tanach Society’  building, the Old Post Office and the ‘Fast’ hotel. The next morning, on the Sabbath, Lehi fighters conquered the tall Notre Dame complex from Arabs who’d occupied it, and were using it to snipe at the city square and public garden which lay between Barclays Bank and the ‘Fast Hotel’. The Notre Dame complex was comprised of two: the primary hospital building on the western side of St. Louis St., and to its east, the Notre Dame-de-Sacre-Coeur Convent. During the battle, this second building was completely demolished. Its flat rooftop was nicknamed ‘The Rooftop of Death’, because it was the site of two out of the four fatalities, and most of those wounded that day. It overlooked nearby Old-City alleys, and despite our fighters having shot numerous Iraqi volunteer soldiers at the beginning of the battle, it remained dominated by taller buildings, from where many Arab fighters were gathered  opening deadly fire from above, on our fighters below. Upon the rooftop, clutching a ‘Bren’ gun pointed at the alleys of the Old City, lay the body of Mordechai-Nissim Halber, Yehoshua. On the following day, May 16,1948, he was temporarily buried at  ‘Sanhedria’ cemetery.

On November 15,1951 Mordechai was laid to rest at the Mount-Herzl military cemetery.