Complex sentence: The second major event the Cossack Brigade played a role in was the 1906 Constitutional Revolution as a result of intense political pressure and rebellion Muzaffar-din-Shah gave in to the rebels, and died shortly after signing the Constitution.
Split into simpler sentences: The second major event the Cossack Brigade played a role in was the 1906 Constitutional Revolution, as a result of intense political pressure and rebellion. Mozaffar ad-Din Shah gave in to the rebels, and died shortly after signing the Constitution.