Complex sentence: Meanwhile, the Army of the Potomac had taken up positions at the south banks of the Chickahominy, and McClellan continued to ask Washington for more troops, as he felt Lee's army "heavily outnumbered" his own.
Split into simpler sentences: Meanwhile, the Army of the Potomac had taken up positions at the south banks of the Chickahominy. McClellan harangued Washington for more troops, as he felt Lee's army "heavily outnumbered" his own.