Daniel was born on August 22, 1919 in Izmir, Turkey, to Aharon Mordechai and Sarah. The family made aliyah in the early 1920s illegally, taking a ship to Beirut, then were smuggled by way of Rosh HaNikra via Nablus to Jerusalem.
They then moved to Neve Zedek in Tel Aviv. His father worked in the film industry, representing Paramount Studios.
Daniel studied in the Herzliya Gymnasium. In grade twelve, he joined the right-wing version of Hagana, and afterwards he moved on to the general Hagana. In 1938, he was sent to guard Kfar Yaavetz. On his return, he became the company secretary in Section 6. Due to the restraint exercised by the Hagana, he returned to its right-wing version, which had already been renamed IZL, serving in Company H in intelligence. With the split of IZL in 1940, he joined Lehi together with his brother Gavriel. Their house on 89 Dizengoff in Tel Aviv was at the organization’s disposal. His father met Yair on one of his overseas trips, forming a connection between Yair and the Masri family. Yair came to console the family when the mother passed away. In their home, the IZL held one of its most important meetings, attempting to repair the tears in the movement, but it failed.
Daniel was active in Lehi’s Intelligence Department. On December 2,1941 he was arrested along with Yitzhak Shamir, Aryeh Boyko, Yizhak and Avraham Siman-Tov, and Yosef Cohen, in Yehoshua Sattler’s apartment. He was transferred to Mizra, and from there to Latrun. On October 19, 1,944 he was exiled to Eritrea, then to Sudan and then back to Eritrea. He was released in June 1946 and returned to Israel. After the bombing of the King David Hotel, he was arrested again, and he sat in Latrun until he was released on Erev Rosh Hashana 1946.
After leaving Latrun, he increased his Lehi activity. He trained new recruits with firearms and was responsible for the training base in Petah Tikva.
In the War of Independence, he served in Battalion 82 of the 8th Brigade, as a squad commander. He served in all the battalion’s battles and was injured at Der Tarif, but he continued to fight and participated in the Battle of Beersheba.
Due to medical reasons, he had to leave the battalion and became a canteen supervisor. After his demobilization, he joined the family business.
Daniel married Tamara Katz, and they had two daughters and numerous grandchildren.