While the army labored to build the upper dam, the navy, more confident of rescue, worked to lighten the loads on the trapped gunboats. From May 10 through 12, the remaining gunboats above the rapids struggled through the upper shoals to the pool behind the main dam. Yet another dam had to be built to refloat a gunboat that got stuck during this passage. Then on the twelfth of May, the _Mound City_, the largest gunboat of the fleet, ran for the gap in the main dam. The previous scene was repeated, with thousands lining the banks to watch the excitement. Marching bands played the “Star Spangled Banner” and the “Battle Cry for Freedom.” Like the _Lexington_ before it, as the _Mound City_ hit the gap, it ground against the rocky river bottom, and then shot through. The next day all of the trapped vessels lay safely below the rapids. THE CAMPAIGN ENDS While Federal troops labored to build the dam, Taylor’s Confederate army was not idle. Some rebels continued to harass the outposts around Alexandria, while others destroyed bridges and blocked roads in an attempt to entrap the Union forces. Federal boats already below the rapids were constantly ambushed along the lower Red River as they attempted to supply the army. In fact, the Confederate soldiers were able to cut off all navigation on the river for a while, isolating the Yankees. On May 13, with all the gunboats now safely below the rapids, Union forces moved out of Alexandria. The Union soldiers left with mixed feelings. They had been beaten in battle, harassed, and almost completely destroyed. They were exhausted. Still, they had accomplished a magnificent feat in building the dam and rescuing the fleet, and some had even made friends among the townsfolk. [Illustration: Admiral Porter’s fleet on the Red River. From _Harper’s Pictorial History of the Civil War_, March 1864. Courtesy of the Library of Congress.] But for the local population this was a critical time. Rumors spread that the town would be torched when the army left. Banks ordered a detail of 500 men to be left behind to protect the town from arson. But fires quickly broke out as soon as the main army was out of town. It is unclear who started the fires, as some accounts describe soldiers looting and setting fires, while other accounts note that army guards shot looters. Probably, both Union troops and local looters were involved. One detachment, the 92nd Colored Infantry who also helped build the dams, was known to have fought a fire for many hours, until the building was doomed and the troops were forced to continue their retreat. One Yankee soldier described the scene: [Illustration: Alexandria, May 1864. Courtesy of the Louisiana State Library.]