 That approach failed following the Union Navy's defeat at the Battle of Drewry's Bluff, about downstream from the Confederate capital, on May 15.Basing artillery on a strategic bluff high above a bend in the river, and sinking boats to create an impassable series of obstacles in the river itself, the Confederates effectively blocked this potential approach to Richmond.McClellan's army moved towards Richmond over the next three weeks, coming to within four miles (6 km) of it.