<Li> Brig. Gen . Edwin V. Sumner </Li> <Li> Brig. Gen . Samuel P. Heintzelman </Li> <Li> Brig. Gen . Erasmus D. Keyes </Li> <P> The Army of the Potomac had approximately 50,000 men at Fort Monroe when McClellan arrived, but this number grew to 121,500 before hostilities began . The army was organized into three corps and other units, as follows: </P>

What was the significance of the peninsula campaign