Complex sentence: Meanwhile Arnold advanced up the James, plundering both sides of the river: in a brutal raid upon Harrison's Berkeley, Arnold intently removed and burned all family portraits to, most effectively personalize the attack on the signer.
Split into simpler sentences: Meanwhile Arnold advanced up the James, wreaking havoc on both sides of the river. In a brutal raid upon Harrison's Berkeley, Arnold intently removed and burned all family portraits, to most effectively personalize the attack on the signer.