Complex sentence: Stepan Dmitrievich Nechaev (1792--1860), general of the Most Holy Synod, was the first one to study the materials about the Kulikovo Field.
Split into simpler sentences: Stepan Dmitrievich Nechaev (1792--1860), general of the Most Holy Synod. Nechaev was the first one to study the materials about the Kulikovo Field.