The XI Corps (Eleventh Army Corps) was a corps of the U.S. Army during the American Civil War, best remembered for its involvement in the battles of Chancellorsville and Gettysburg in 1863. The corps was composed primarily of German-American regiments. Formation and the Valley Campaign The XI Corps was an amalgamation of two separate commands. These were John Fremont's Army of the Mountain Department and Louis Blenker's division of German immigrants. Blenker had led a German brigade at First Bull Run, although it was held in reserve and saw no major fighting, and afterward became a division commander in the new Army of the Potomac. Intended to go to the Virginia Peninsula in the spring of 1862, Blenker's troops were instead detached and sent out west to join Fremont. The division got lost and ran out of supplies, resulting in soldiers dropping out of the ranks from hunger, fatigue, and sickness. Many German soldiers angered locals in the Shenandoah Valley by indiscriminately looting homes and farms. They also did not have a good relationship with the native-born soldiers in Fremont's command—eventually, Brig. Gen William Rosecrans found the lost division and brought them to Fremont's headquarters at Petersburg, West Virginia. At the Battle of McDowell on May 5, Robert Schneck's division unsuccessfully attacked Stonewall Jackson's army. On June 8, Fremont's entire command engaged Jackson again at the Battle of Cross Keys, where Blenker's German troops were routed from the field in their first battle. By the end of the month, Brig. Gen Carl Schurz wrote to President Lincoln that the German regiments suffered from hunger, lack of tents and shoes, and could barely fight. Of the 10,000 men Blenker had had with him in March, less than 7000 were still present for duty in late June. On June 26, 1862, President Abraham Lincoln ordered that "the troops of the Mountain Department, heretofore under the command of General John C. Frémont, shall constitute the First Army Corps, under the command of General Frémont." The corps thus formed was, for the most part, the same as the one afterward known as the XI Corps, and within a short time, it was officially designated as such. This order of President Lincoln was included in the one constituting John Pope's Army of Virginia, which was formed from the three commands of Frémont, Nathaniel P. Banks, and Irvin McDowell. Fremont was offended at serving under Pope,