Addis bm.  At the start of the American Civil War in early 1861, Rucker declined appointment as a major in the 6th Cavalry so he could continue serving as a quartermaster.[16] In August 1861, he was promoted to major in the Quartermaster Corps and assigned to command the Washington, D.C. Quartermaster Depot.[16] In September 1861, he was promoted to colonel of Volunteers as an additional aide-de-camp to General George B. McClellan, an appointment he carried out while continuing to command Washington Depot.[16] Rucker remained in command through the end of the war, during which Washington Depot handled the majority of food, equipment, and supplies provided to the Union Army in the Eastern Theater of the American Civil War.[16] In May 1863, he was promoted to brigadier general of Volunteers.[17]When Confederate forces threatened Washington, D.C. in the summer of 1864, Rucker participated in the Civil War Defenses of Washington by organizing available quartermaster soldiers as the First Brigade, which he commanded in and around Fort Stevens.[18] In July 1864, Rucker received brevet promotions to lieutenant colonel, colonel, and brigadier general in the Regular Army.[16] In March 1865, he received promotion to brevet major general of Volunteers.[16] After the war, Rucker oversaw the sale at auction of surplus animals and equipment that were no longer needed, the allocation of remaining supplies and equipment to various Army posts, and the downsizing of the Quartermaster Corps.[16]Following the Assassination of Abraham Lincoln, on April 15, 1865, Rucker procured a coffin and provided a contingent of soldiers so Lincoln's remains could be carried from the Petersen House.[19] After the soldiers brought Lincoln's body from the house to a waiting cart, Rucker led a detachment of infantry and cavalry as they escorted the coffin to the White House.[20] Afterwards, Rucker was among those who remained in the second-floor guest room when surgeon Joseph Janvier Woodward conducted an autopsy.[20]Post–Civil WarIn July 1866, Rucker was promoted to colonel in the Regular Army and assigned as the Army's Assistant Quartermaster General.[16] In September of that year, he received brevet promotions to brigadier general and major general in the Regular Army in recognition of his performance during the Civil War.[21] Rucker was assigned as Chief Quartermaster of the Department of the East in 1868.[22] In 1869, he was assigned as Chief Quartermaster for the Military Division of the Missouri, with headquarters in Chicago.[23] In 1875, Rucker was assigned to command of the Philadelphia Quartermaster Depot, and he served in this post until 1882.[16]On February 13, 1882, Rucker was promoted to brigadier general and assigned as Quartermaster General of the United States Army.[16] At the same time, he applied for retirement.[16] His request was approved, and he retired due to age on February 23.[16]