As darkness and dense fog set in on July 18, Morgan's men stopped to rest in fields near Portland while Lieutenant Commander Leroy Fitch and the tinclad U.S.S. Moose headed upstream from Pomeroy and anchored near the ford at the southern tip of Buffington Island. At sunrise, Fitch awoke to gunfire as Judah's men attacked the Confederates, and as the fog lifted, enemy horsemen could be seen crossing the river. Gun crews fired on the escaping raiders, killing several and driving some back toward shore, and only about 30 crossed the ford to the relative safety of West Virginia. Fitch then ordered shells fired over the river bluff and onto the battlefield, causing more confusion than deaths as Union and Confederate soldiers rode wildly across the fields to avoid the bursting shells. In the turmoil, Judah's and Hobson's forces closed in, Morgan's troops were surrounded on three sides and caught in a crossfire, and with the ford blocked, the raiders were forced to ride north in search of another crossing point. During the Civil War, the Union sought control of key trade and supply routes by building, converting, or purchasing gunboats to capture and control major and minor rivers across the South and central United States, especially the Ohio and Mississippi rivers, to block trade and troop movement between the eastern and western parts of the Confederacy while preserving Union access to the rivers.