Liberation of R. Yosef Yitzchak (1927)
On the 12th of Tammuz of 1927, the sixth Lubavitcher rebbe, Rabbi Yosef Yitzchak Schneersohn, was officially granted release from his sentence of exile to Kastroma in the interior of Russia.
Twenty-seven days earlier, the Rebbe had been arrested by agents of the GPU and the Yevsektzia ("Jewish Section" of the Communist Party) for his activities to preserve Judaism throughout the Soviet empire and sentenced to death, G-d forbid. International pressure forced the Soviets to commute the sentence to exile and, subsequently, to release him completely. The actual release took place on Tammuz 13, and Tammuz 12-13 is celebrated as a "festival of liberation" by the Chabad-Lubavitch community.
Tammuz 12 is also Rabbi Yosef Yitzchak's birthday