He taught, guided, and inspired thousands of disciples throughout his lifetime, by word and deed, with legendary diligence and intensity in Torah study.

The Mirrer rosh yeshiva, Eliezer Yehuda Finkel, set his sights on Shmuelevitz as his eventual spiritual heir.

Shmuelevitz married Chana Miriam,[5] the rosh yeshiva's daughter, on the last day of Hanukkah, 3 Tevet 5690 (3 January 1930).

The hallmark of his lectures was depth combined with breadth; it was not uncommon for him to cite 20 or 30 different sources from far-flung corners of the Talmud and its commentaries during a single class.

The students and faculty fled from Mir to Vilna, where they stayed for about two months, after which they moved to Keidan, where they managed to set up the yeshiva once more in 1940.

After being ordered out of Keidan seven months later by the Communist authorities, the yeshiva divided into four groups,[7][8] each numbering between eighty and one hundred students.

In late 1940, hundreds of Mir yeshiva students obtained visas from Chiune Sugihara to travel via Siberia and Vladivostok to Japan.

[1] This was despite the fact that exchanging foreign currency in Shanghai was fraught with danger and Shmuelevitz lived with a perpetual fear of being apprehended by the authorities.

During the Six-Day War, when the yeshiva was within range of Jordanian artillery fire, Shmuelevitz sent some of the manuscripts to America with his uncle, Avraham Yoffen, with specific instructions that he carry them by hand and not put them in his luggage, because, "Dos iz meyn gantze leben (This is my whole life)."

[11][12] A few days after Sukkot 1978, Shmuelevitz was rushed to the hospital and, for the next two months, was gravely ill. Moshe Feinstein said, "The world rested upon Reb Chaim's shoulders."

During his lifetime, Shmuelevitz committed to paper his every lecture and public address, leaving behind at his death thousands of handwritten pages, including chiddushim on every tractate of the Talmud.