Rabbi Yitzchak Menachem Mendel Danziger, the last Rebbe of Alexander, known as the Akeidat Yitzchak, was born in Alexander in 1880. He was the son of Rabbi Shmuel Tzvi, the third Rebbe of Alexander and author of Tiferet Shmuel, and grandson of Rabbi Yechiel Danziger, the founder of the dynasty. From childhood he stood out for his sharp mind and diligence; he studied under his uncle, the Yismach Yisrael, the second Rebbe of Alexander, and then under his father.

He became Rebbe in 1924 on his father's death and led Alexander Chassidism, one of the largest in Poland with tens of thousands of followers: thousands of Chassidim came to him for the Seder and the High Holy Days, and hundreds every Shabbat. He stressed humility, love of every Jew, drawing close those who were distant, daily charity and communal prayer. He founded the Beit Yisrael network of Alexander yeshivot throughout Poland, lived in great simplicity and spent most of his days studying the revealed and hidden Torah.

His teachings were published as Akeidat Yitzchak. He was murdered in the Holocaust at Treblinka on 23 Elul 5702 (1942), together with most of his Chassidim.