After the passing of Rabbi Shneur Zalman in 1813, his son Rabbi DovBer (Rabbi Menachem Mendel's uncle and father-in-law) was appointed his successor. At this time Rabbi Menachem Mendel commenced a period of fourteen years seclusion, during which he devoted himself to study and prayer. He emerged to play his part in public life in 1826, at the time when Rabbi DovBer was accused of subversive activities. His first undertaking was the organization of a committee to defend Rabbi DovBer.

When Rabbi DovBer passed away in 1827, the Chassidim called upon Rabbi Menachem Mendel to accept the leadership of the Chabad-Lubavitch movement. For many months he rejected the tremendous responsibility of this position, but finally, he reluctantly answered the call.

Rabbi Menachem Mendel was a prolific writer. His works contain a unique synthesis of the "esoteric" and "exoteric" aspects of Torah — Talmudic, Midrashic, Kabbalistic and Chassidic thought are harmoniously and lucidly blended. He would certainly have liked nothing better than to continue his writings, edit the works of his grandfather and father-in-law, and lead the tens of thousands of Chassidim who had swelled the ranks of Lubavitch. But this era had its own share of problems with which Jews were confronted.

Jews in Russia were barred from most occupations and business opportunities, and poverty was rampant among them. Deeply interested in the economic position of the Jewish people, Rabbi Menachem Mendel advised the Chassidim to engage in agriculture wherever possible, and he gave financial aid to those who followed his advice.

At that time it was the policy of the Russian government to make it difficult for Jews to settle in the villages, so Rabbi Menachem Mendel bought a large tract of land near the city of Minsk on which to settle many Jewish families. In 1844 he purchased another large area of land with some adjoining forests in Minsk Province from Prince Shzedrinov, and established the settlement of Shzedrin. A council was organized to direct its affairs.

The founding of Shzedrin made a deep impression on Jews and non-Jews alike. In a government report from the official of the Province of Minsk to the Minister of Interior, they spoke of Rabbi Schneersohn of the city of Lubavitch with respect and praise. The report mentioned that he had acquired a large tract of land and established there a settlement for Jews, thereby raising their living conditions and improving their position. It also spoke of the great influence of the Rabbi of Lubavitch on all the Jews living within "the pale of [Jewish] settlement" of the Russian Empire and of the manner in which he constantly tried to improve their material living conditions.

In 1827, the infamous Czar Nicholas I instituted the "Cantonist" edict, which introduced the conscription of children for military training and service. Originally it applied to children of the age of twelve years old and older. The Jewish communities had to supply a quota of ten children per thousand (non-Jews had a smaller quota and more liberal exemptions).

The children were sent away by government officials and distributed among the peasantry, or sent to special schools until the age of eighteen. They were then removed to barracks for military service for twenty-five years. This meant that the children were torn from home and from cheder for the greater part of their lives, and were subjected to treatment calculated to estrange them from their own people.

No parent would willingly yield a child for such a callous scheme, but the community was obliged to provide its quota. This led to the appearance of a despicable character, the "catcher," whose job was to catch or kidnap the children and hand them over to the government officials. Heart-breaking scenes, with children being torn from their mother's arms, became commonplace. The brunt of the tragedy fell upon the poorer Jews, who were unable to buy their children's freedom from the "catchers."

Rabbi Menachem Mendel attacked the problem without regard to the dangers involved. It was necessary to save as many as possible of the children who were actually conscripted. With this in view the Rebbe organized a special council for the following three purposes:

First, to study the position of the individual Jewish communities, with a view to helping them decrease the number of children they would have to supply.

Second, to engage in freeing those who had been captured. It was arranged to achieve this through the organization of a special clandestine society known as Techiat Hameitim ("revivers of the dead"). The method employed was to pay a ransom for each child to the officials concerned. They would return the child, at the same time reporting to the authorities that the child in question had died during the journey. They would also officially inform the community concerned of the death of the child. These "death certificates" brought great happiness to the parents. Obviously, the "dead" children had to be hidden for a long time (hence the name, Techiat Hameitim Society). They were then sent to cheders or Talmud Torahs far from their home towns.

Third, to send special trustworthy people to the places where the cantonist children were stationed to encourage and urge them to remain faithful to their religion and to their people.

Apart from the huge expense it involved, this responsible work was highly dangerous, for it amounted to an act of treason. Yet this underground program was successfully carried out and was never betrayed.

At the same time, Rabbi Menachem Mendel concentrated his efforts on supporting the agricultural centers in the districts of Vitebsk and Minsk. He dispatched Rabbi Hillel of Paritch, one of the leading Chassidim, to the settlements in the district of Kherson, where he spent several months each summer.

Besides instructing the Jews there in the study of the Torah and the fear of G‑d in accordance with Chassidic teachings, he inspired them to rise to a high level of brotherly love, mutual help and generally high moral conduct.

During the twelve years from 1827-1839, Rabbi Menachem Mendel concentrated his efforts on communal activities in the field of material aid; the protection of Jewish children from kidnappers and their maintenance in safety, and spiritual help for the cantonists.

Rabbi Menachem Mendel devoted particular attention to the requirements of the Jewish conscripts in the Russian army. He ensured that there should be special representatives at every place where Jewish troops were stationed, with the specific aim of concerning themselves with the troops' moral conduct. These representatives were to encourage the soldiers and strengthen them from falling into the traps of conversion to Christianity laid for them by eager missionaries.

Rabbi Menachem Mendel also worked for the support of needy Torah scholars studying at the Yeshivahs and advanced institutes of learning.

During all these years he carried on his work without any interference from the opponents of Chassidism, in either the religious ("Mitnagdim") or the so-called "enlightened" groups in Russia ("Maskilim"). During this time also, there was no conflict between Chassidim and Mitnagdim. On Rabbi Menachem Mendel's frequent visits to Chassidic communities in Minsk and Vilna, the Mitnagdim always accorded him great honor and attended his chassidic and talmudic discourses.