Civil War Union Brigadier General, US Diplomat. He was born in Lancaster, Ohio, into Ohio's privileged Ewing family (his father was Thomas Ewing, who served as a United States Senator and Cabinet member of several presidential administrations). His brothers were future Union generals Charles, and Thomas Junior, and his foster brother and later brother-in-law was William T. Sherman. He started life as a worry to his kin. Privately tutored at home, he entered the United States Military Academy at West Point with its 1848 class but, failing the engineering exams, was compelled to resign before graduation. He joined the gold rush of 1849 but found no gold and came east in 1852, setting up a law practice in St. Louis, then trying to establish one in Leavenworth, Kansas, with the help from his brother Tom and William T. Sherman. After returning to Ohio in 1858, he received his first opportunity to exercise public responsibility in May 1861, when Ohio Governor William Dennison, a political associate of Hugh's family, appointed him brigade inspector of state volunteers. He soon served under Generals George B. McClellan and William S. Rosecrans in the first western Virginia campaigning, and was appointed Colonel of the 30th Ohio Volunteer Infantry on August 20 1861. After the reorganization and reassignment of state troops, he was sent to the Army of the Potomac, in which he received favorable notice for his bravery at the Battle of South Mountain and at the Battle of Antietam. In this theater he successively led a regiment, then a brigade of the IX Corps, and was appointed a Brigadier General of Volunteers on November 29, 1862. During the Second Vicksburg Campaign, he served under Major General Sherman in the XV Corps, capable performance won him command of Brigadier General William Sooy Smith's old XVI Corps division, which had been transferred to the XV Corps. He then took command of the XV Corps' 4th Division and led it through the Tennessee fighting. At the Battle of Missionary Ridge at Chattanooga, his command headed the army's assault on Confederate Major General Patrick R. Cleburne's line. The Confederates were committed to desperate defense, hit his men with all their available ordnance, then pelted them with rocks and debris. When the Confederates retreated to Georgia, he was given charge of the occupation forces in Louisville, Kentucky. After a year of this duty he rejoined Sherman's army, then in North Carolina, and began plans for a thrust up the Roanoke River in the Confederate rear, but the war ended before this could happen, and he was mustered out of volunteer service on January 15, 1866. He also was brevetted Major General, US Volunteers for more than 4 years of service. His war record won him influence in peacetime. Appointed United States Minister to Holland, he served there until 1870. After a brief period practicing law in Washington D.C., in the early 1870s, he moved to a farm near Lancaster, Ohio, and pursued a career as a writer until his death there.