Moshe Tzvi was born in 1904 in Poltava, Ukraine, to Avraham Mordechai HaLevi Segal and Hannah Leah bat Nahum Mencken. He studied in cheder, as well as the yeshivot of Mir and Lubavitch. When the Communists took over the country, he could not find work, as he was not a member of the Communist Youth. He was able to find a job finally teaching Torah secretly and arranging a group of Tze’irei Zion and HeHalutz, whom he sent for training to the Jewish villages near Nikolayev and Odessa. In 1924, he made aliyah with his parents to the Land of Israel. He worked in construction, in a factory for mosaics and marble; as an agricultural worker; and as a guard in the south, the Jordan Valley and Jerusalem. For a short time, he worked in the offices of the National Committee. In 1931, he married Rachel bat Shlomo Yaakov Korovsky.
Moshe Tzvi dedicated himself to protecting the Yishuv and fighting for its rights and national liberation. In 1926, he participated in a demonstration at the Western Wall. As Yom Kippur 1930 ended, he was the first to defy the Mandatory ban on blowing a shofar by the Western Wall, even though dozens of British police were stationed there. He was immediately arrested and sent to the Kishleh, but he was released when Chief Rabbi A. I. Kook, moved by the bravery of his act, advocated for him. Moshe Tzvi was a member of the Hagana, and when the riots broke out in 1936, he was responsible for guarding North Tel Aviv. He participated in the protests against the decrees of the Mandate.
In 1937, he founded Brit Hashmona’im, a Religious Zionist youth movement, and he stood at its head until it was disbanded when the State was established. He joined the IZL; after the split in 1940, he became part of the command staff, but he soon left for Lehi.
He was responsible for the Jerusalem chapter and was very active in recruiting new members, mainly from the ranks of Brit Hashmona’im. In his house, Lehi escapees from prison found refuge. After the State was established, he went out to settle Kfar Habad, where he establsiehd a farm and served as the secretary of the village, being very active in building and expanding it. He became the secretary of the local council of Lod Valley, and he was active in Tze’irei Habad. Later, he was part of the Temple Mount Faithful. He published a number of writings over the years: The Guard’s Diaries, from his period as a guard in the Galilee (in Doar HaYom) and Musings in Jewish Thought (in the monthly HaHashmona’i). He also wrote in various dailies.
Moshe Tzvi had three sons and four daughters, as well as numerous grandchildren.
He passed away on Yom Kippur 1985, and he was buried on the Mount of Olives.