Complex sentence: Numerous raids were conducted and battles fought in attempts to cut off the railroad supply lines through Petersburg to Richmond, and many of these caused the lengthening of the trench lines, overloading dwindling Confederate resources.
Split into simpler sentences: Numerous raids were conducted and battles fought in attempts to cut off the Richmond and Petersburg Railroad. Many of these battles caused the lengthening of the trench lines, overloading dwindling Confederate resources.