Modest Petrovich Mussorgsky (March 21 [O.S. March 9] 1839 – March 28 [O.S. March 16] 1881) was born into a wealthy rural, landowning family. He began by picking out on the piano the tunes he heard from the serfs on his family’s estate. At the age of six, he began to study piano with his mother. His parents initially set him out on the career of military officer. He became a cadet and finally commissioned in an elite imperial regiment. Two years later, in 1858, he resigned his commission. During this time, he met a musically-inclined army doctor: Alexander Borodin. The two became friends. In 1861, with Russia’s emancipation of the serfs, his family lost significant income, and he was forced to earn a living. In 1863, he began a spotty career in the civil service…In 1856, he met the composer Dargomïzhsky, who in turn introduced him to Cesar Cui, Mily Balakirev, and a critic named Victor Stasov. Gradually, Borodin and Nicolai Rimsky-Korsakoff joined to form a loose group known as the “Moguchaya Kuchka” (“the mighty handful” or “the mighty bunch”).
http://www.classical.net/music/comp.lst/mussorgsky.php

See also: https://schristywolfe.com/2015/05/05/viktor-hartmann-born-may-5-1834/