Halberstam became one of the youngest rebbes in Europe, leading thousands of followers in the town of Klausenberg, Romania, before World War II. His wife, eleven children and most of his followers were murdered by the Nazis while he was incarcerated in several concentration camps. After the war, he rebuilt Jewish communal life in the displaced persons camps of Western Europe, re-established his dynasty in the United States and Israel, and rebuilt his own family with a second marriage and the birth of seven more children.
Yekusiel Yehudah was orphaned of his father at the age of 13. Afterwards he studied with other leading Hasidic rebbes, including Rabbi Myer Yechiel of Ostrovtza, Rabbi Chaim Elazar Shapiro (the Munkatcher Rebbe), and his great-uncle, Rabbi Shalom Eliezer Halberstam of Ratzfert. During this period, Yekusiel Yehudah became known as the "ilui ("genius") of Rudnik,". In later years he would periodically return to Rudnik to visit with his followers, who remained loyal to him even after the appointment of his first cousin Rabbi Benyumin Teitelbaum-Halberstam as Rabbi in 1924.
In 1921, Halberstam married his second-cousin Chana Teitelbaum, the daughter of Rabbi Chaim Tzvi Teitelbaum, the Rabbi of Sighet, Romania. She was also a descendant of the Divrei Chaim: her grandfather, Rabbi Sholom Eliezer Halberstam, was one of the seven sons of the Sanzer Rav. The young couple lived in her father's house for the next five years.
In 1927, at the age of 22, Halberstam accepted the post of Rabbi of Klausenberg, the capital city of Transylvania (western Romania). Although he was relatively young, he impressed the largely non-religious community with his charismatic personality, wisdom, and warmth toward Jews of all backgrounds. During the 16 years that Halberstam led the Klausenberg community, he exhibited many of the qualities that would set him apart during his imprisonment by the Nazis. He slept only three hours a night, often on a synagogue bench, and he often ate only one meal a day, reserving bread for the Sabbath. He spent much of his day in prayer and study. His love for and faith in God was legendary. He also paid special attention to children, founding a yeshivah in which 100 students learned in Klausenberg.
The Rebbe's reputation spread throughout Romania and Hungary, and even reached Israel. In 1937 Halberstam was offered a seat on the Jerusalem rabbinical court. Uncertain as to whether he should accept the seat or stay with his community, Halberstam wrote to his mother in Rudnik for advice. She advised him to stay where he was, saying he was too young to accept such a position.
Halberstam also received recognition for his uncompromising positions on traditional Judaism and his opposition to Zionism, and his disagreements with the Hungarian Mizrahi leadership. He often clashed with the large Conservative community in Budapest and with some Zionist leaders like Dr. Rudolf Kasztner, and his son-in-law, Dr. Josef Fischer.
In 1941, a new law required all Jews living in Hungary to prove that their family had lived in and paid taxes in Hungary back to 1851. Suddenly thousands of Jews, including the Rebbe (who was born in Poland), were placed in jeopardy. The Rebbe, his wife and eleven children were arrested and brought to Budapest, where the family was separated. The Rebbe was jailed with a group of leaders who were eventually sent directly to Auschwitz. Thanks to the efforts of friends and supporters, the Rebbe was released and the family returned to Klausenberg.
Despite the danger, the Rebbe refused to leave his followers and made no effort to save himself from further searches. Instead, he threw himself into helping refugees from Nazi-occupied lands and tending to his followers. Between 1941 and 1944, the Rebbe never stopped studying Torah and praying for the Jewish people.
On March 19, 1944 the Germans invaded Hungary and Gestapo chief Adolf Eichmann immediately organized the round-up, ghettoization, and deportation of Hungarian Jews to Auschwitz. The Klausenberg ghetto was established on May 1, 1944, and was liquidated via six transports to Auschwitz between late May and early June. Knowing that the Gestapo targeted community leaders first, the Rebbe hid in an open grave in a cemetery for several weeks. He then fled to the town of Banya, where he was conscripted into a forced-labor camp along with 5000 other Hungarian Jews. Though hunger was not a problem here—the barbed-wire enclosure had a back exit through which Jews could buy bread and milk from non-Jews—the Hungarian soldiers constantly badgered and searched inmates for their valuables. The Rebbe was forced to shave his beard, but he did not lose his composure or faith in God. He continued to conduct prayer services and even a Shabbat tisch.
In Auschwitz, Halberstam seemed to live in another world. The bits of food that other prisoners hungered for and fought over were, in the Rebbe's eyes, less important than their use for mitzvot. He decided early on to try to keep every Torah commandment he could, and even the minhagim that he had learned from his forefathers. Thus, he would often choose to use the bit of water he had to wash his hands for prayer, rather than to wash his hands to eat. He never touched non-kosher food and refused to eat food cooked in a non-kosher pot. Often he went hungry. His staunch faith gave spiritual strength to many. He assured his fellow inmates that God was with them in the valley of death, and would not abandon them.
In 1944, a year after the Warsaw Ghetto uprising, Halberstam was assigned to a special labor detail to clear out the ruined ghetto. He and 6000 other prisoners searched for valuables and demolished the ruins by hand and with rudimentary tools so that the Nazis could sell the bricks and steel to Polish contractors. As they beheld skeletons piled in the street, and uncovered bunkers in which Jews had died by gas or shooting, the Hungarian prisoners realized for the first time the extent of the annihilation of European Jewry.
This time the Rebbe did not shave his beard, which is considered a mark of holiness for Hasidim. He wrapped his beard and face in a handkerchief, pretending he had a toothache. This charade was accompanied by the fact that he cried all day as he worked, praying and communing with God.
When the prisoners began to hear rumors that their labor detail was about to be liquidated, they decided to try to escape rather than let the Nazis kill them. However, the Rebbe encouraged them to adopt a "wait and see" attitude. In response to one plan, in which prisoners would storm the camp gates and make a run for the forest, where they would connect with partisans, the Rebbe advised, "Until we see that the Nazis are about to exterminate us, it is prohibited for anyone to sacrifice his life and put himself in a situation of certain death. But one must remain vigilant, and as soon as it becomes clear that the Nazis are ready to attack us, we must do everything in our power to rise up against them." The prisoners decided to follow his advice. Some time later, after most of the prisoners had been transported from Warsaw, 500 remaining prisoners did stage a revolt. The Nazis killed every one of them.
As the Russian Army moved closer to Poland, the Germans decided to liquidate the special ghetto-clearing unit of which Halberstam was a member. All the prisoners were taken to a field outside of Warsaw, told to undress and stand near open pits, where soldiers prepared to machine-gun them. At the last moment, however, a car sped into the field. A high-ranking officer jumped out and communicated the special order from Berlin to stop the execution and send the prisoners to the Dachau concentration camp, where they were needed as slave laborers.
This unexpected reprieve, however, led to a brutal death march. For the next week, the prisoners were forced by SS soldiers wielding wooden clubs and steel bars to march 21 miles a day at top speed. In the blazing July heat, the emaciated prisoners were deprived of food and water and allowed to rest only at night. Those who couldn't keep up were shot.
On the third day, strained to the length of their endurance, the group was finally brought to rest for the night in a field surrounded by SS officers. As the guards slept, the Rebbe passed the word around: "Everyone should dig beneath himself. God's salvation comes in the blink of an eye." Each prisoner began to dig with his fingers, spoons, or pieces of wood. Remarkably, each found water, and small springs began to pop up everywhere, quenching everyone's thirst and giving them new life.
On the fifth day, the surviving marchers were packed into cattle cars for the rest of the journey to Dachau. Over the next few days, many succumbed to the overcrowding, lack of water, stench and heat in the cattle cars. Of the 6000 that set out on the death march, less than 2000 made it to Dachau alive. The Rebbe was one of the survivors.
Despite the hardships and privations, Halberstam was a beacon of strength and hope for his fellow prisoners. When one died in the infirmary—hardly a noteworthy occurrence in those days—the Rebbe stood up and eulogized him for having been a great Torah scholar in Hungary. He refused to eat non-kosher food or food cooked in the non-kosher kitchen, subsisting only on bread and water during his nine months in Muldorf. Moreover, he would not eat the bread until he had ritually washed his hands, and would often wait for days to find some water for this purpose. One prisoner watched him stand beside the cement mixer for hours at a time, collecting the drops of water that dripped from the tank.
As the war wound down in spring 1945, the Germans disbanded the Muldorf camp and sent the inmate population on yet another death march, chasing them from place to place without food or rest. Sometimes they were loaded aboard rail cars and driven to and fro. On Friday, April 27, the train suddenly stopped in a small town and SS officers jumped aboard, declaring, "You are free!" and ripping the Wehrmacht badges from their uniforms. Many prisoners believed them and jumped off the train. But Halberstam told the people around him, "Today is the eve of Shabbat. Where will we go?" Then he added, "My heart tells me that not everything here is as it should be." Suddenly, SS soldiers rode in on bicycles from all directions, firing machine guns and killing hundreds of people. At the same time, American bombers dove in, strafing the field. Only Halberstam and those who stayed with him on the train escaped injury. Two days later, their real liberation came when the train stopped near a village and the Nazi guards deserted them. American soldiers boarded the train with smiles, candy and chocolates.
The group was brought to the Feldafing DP camp in Munich, exhausted, demoralized and penniless. Here Halberstam's leadership qualities rose to the fore and he became the spokesman and leader of the religious survivors. He immediately arranged for the proper burial of those who had died by the train tracks, and demanded kosher food for the survivors. On the first Shabbat after liberation, he led the public prayer services in a newly-opened synagogue and delivered a two-hour lecture, quoting from memory scholarly writings that he had last seen years before.
Halberstam's wife and ten of his children were murdered by the Nazis during World War II. His eldest son survived the war, but succumbed to illness in a nearby DP camp before his father even knew that he had survived. Yet Halberstam never complained of his lot, and avoided depression by reaching out to others. He spent much time listening to and comforting people of all ages, and brought hundreds of people back to religious observance through his passionate public speeches.
On Yom Kippur, 1945, General Dwight D. Eisenhower visited the camps and came to see Halberstam, who had received a reputation as a "wonder rabbi". However, the Rebbe would not speak with him until he had finished his prayers. Afterwards he told the general, "I was praying before the General of Generals, King of Kings, the Holy One, Blessed be He. The earthly general had to wait." Impressed by the rabbi's leadership and frankness, Eisenhower asked him if there was any way he could help him in his efforts. In typical fashion, Halberstam asked for a small sample of the Four Species so that the survivors could properly celebrate the upcoming Sukkot holiday.
In spring 1946 the Rebbe made a special fund-raising trip to New York on behalf of She'eris HaPleita, raising $100,000, a huge sum in those days. That fall, he embarked on another fund-raising trip and decided to resettle in New York to strengthen the American Jewish community there and to continue working for Holocaust survivors from that side of the Atlantic. He established his court in the Williamsburg section of Brooklyn.
In 1947 he married his second wife, Chaya Nechama Ungar, the daughter of the Nitra Rav, Rabbi Shmuel Dovid Ungar, and rebuilt his own family with the birth of five daughters and two sons.
The Rebbe's decision to move to the United States was not a permanent one. Throughout his travails in the Holocaust, he always had in mind the goal of settling in Israel. Toward that end, he established the Kiryat Sanz neighborhood in the beachside city of Netanya in 1957. In so doing, he was the first Rebbe to establish a Haredi neighborhood in an Israeli development town. Over the next few years, he raised money for the establishment of key institutions to serve this neighborhood, including girls' and boys' schools and yeshivas, an orphanage, and an old-age home. He also laid the cornerstone for a community hospital to be run according to the strictest standards of Halakha. This hospital, which would eventually take the name of two donors from England, the Laniado brothers, opened in 1976; today it encompasses two medical centers, a children’s hospital, a geriatric center and a nursing school, serving a regional population of over 250,000.
The Rebbe moved to Israel in 1960, settling in Netanya and directing both the community there and in Williamsburg. He also founded battei medrash and schools in other cities in Israel, and established the Kiryat Sanz neighborhood of Jerusalem as well.
In 1968 he founded yet another Sanz community in Union City, New Jersey, and afterwards divided his time between that community and his residence in Netanya.
The Rebbe recorded his Torah novellae in Shefa Chayim and She'eilos Uteshuvos Divrei Yatziv.
Halberstam died on June 18, 1994, and was buried in Netanya. In his will, he divided leadership of the Sanzer Hasidim between his two sons, His elder son, Zvi Elimelech Halberstam, became the Sanz-Klausenberger Rebbe (also known as the Sanzer Rebbe) of Netanya, and Samuel David Halberstam became the Sanz-Klausenberger Rebbe of Brooklyn.