Rav Yitzchak Menachem was raised and educated by his grandfather, Rav Yechiel of Alexander, founder of the dynasty; by his uncle, Rav Yerachmiel Yisroel Yitzchok, author of the famed sefer, Yismach Yisroel; and by his father.
In תרפ"ד, he was appointed rebbe. At the time, Alexander was the second largest chassidus in Poland. Its adherents numbered in the thousands, and they all accepted his authority unquestionably. Only a small number clung to his uncle Rav Betzalel Yair of Lodz. Rav Yitzchok Menachem initially refused to serve as rebbe insisting that his brothers were more worthy, however, the rabbonim among Chassidei Alexander, numbering some seventy sages, insisted that he accept the mantle of leadership, and so he agreed.
Similar to the rebbes in the Gerrer Dynasty, he refused to sit at the head of the table and also refused to sit in the same seat for davening that his father or grandfather had previously occupied.
Rav Yitzchok Menachem continued the path of ahavas Yisroel as championed by the Vorker Rebbe from which the Alexander Dynasty hails. Every person was greeted with love and affection. His prayers were accompanied by tears and heart-rending sighs. The same occurred during the singing of zemiros.
As rebbe, his influence was immense. His answers to questions were clear and sharp. His memory was phenomenal and was able to recall by heart entire pages of Shas. He also remembered the names of thousands of his followers, and their families. He kept in touch with chassidim from distant places by sending letters on a consistent basis. He was punctilious about davening with a minyan and he wrote much about this topic to the chassidim.
He established the Alexander Yeshiva which eventually developed into a network across all of Poland named Beis Yisroel named after his grandfather, author of Yismach Yisroel. The yeshiva’s student body consisted of more than 300 students. At the head of the yeshiva stood the rebbe’s brother, Rav Avrohom Chaim Dantziger. A similar yeshiva was established in Yerushalyim as well. Especially well-known was the Lodz branch of the yeshiva which became the center for all of Alexander chassidus. The yeshiva published several newsletters and pamphlets. After the death of Rav Yaakov Pinchos Shraga, the rebbe’s son, the newsletter was named in his memory: “Nehora Shraga.”
As did his father before him, he refrained from any politics and Chassidei Alexander were known to be neutral during all the elections. Wherever they were concentrated and their vote carried power, they formed their own party. In תרצ"ז, the rebbe participated in the Third World Congress of Agudas Yisroel and he was welcomed with great fanfare. When he spoke there, he cried: “What should we say; Am Yisroel is at a very low state, physically and spiritually and there are evil decrees against us that touch upon the primary precepts of our religion. It is just as at the Exodus where there was a wall of fire against us, and we have no were else to turn but to set our eyes up to the heavens.”
When the Nazis entered Poland, he fled Alexander for Lodz where the greatest concentration of chassidim were to be found. From there, he fled to Warsaw, and for two years he lived in the ghetto officially employed as a shoe cobbler at the Schultz store
