Simplify the following text for a Grade 9 native English-speaking person.
Original: He was the Secretary and leading theorist of the Moscow Federation of Anarchist Groups , which was formed in March 1917 after the abdication of Tsar Nicholas II and was primarily concerned with disseminating propaganda to Moscow 's poorer classes .
Simplified: He was also Secretary of the Moscow Federation of Anarchist Groups , which was formed in March , 1917 .