Another of my great, great grandfathers was William Alexander Harmon - as far as I know, his Civil War service was of a week's duration. At least four of William's brothers also served in the Union Army.
The Harmon men were sons of James Harmon and Philadelphia Dickerson, whose fathers had both served in the Revolution.
Robert John Harmon, the fourth child but the eldest son, was born 21 Feb 1824, Marion County, Indiana. He enlisted as a private in Company A, 86th Indiana Infantry on 1 Aug 1862; he was discharged 2 Jan 1863. Possibly his enlistment was only for three months, he may also have suffered an injury or illness. On 13 Jun 1881, Robert J. Harmon applied for his invalid pension which he did receive. He died 1900 in Oklahoma and his wife, Sarah (Dye) Harmon then applied for her widow's pension. This is a file I have not yet obtained from the National Archives.
William Alexander Harmon, was born 7 Jan 1826, Marion County, and married on 17 Jun 1847 in Boone County, Indiana, to Emma Elizabeth Miller. By the time of the War they had five children. William enlisted on 7 Oct 1863, as a Private in Company G, Indiana, 102nd Infanty Regiment, 10 Jul 1863, and was mustered out a week later, on 17 Jul 1863, at Indianapolis. This was a minute men regiment called up for citizens' defense when word was received that a Confederate force of 6,000 cavalry had crossed the Ohio River and was moving on Corydon. The 102nd was organized in Boone County and numbered 623 men. It left Indianapolis the next day by rail, traveling to Vernon, where Company K was mounted and sent in pursuit of the enemy. The unit was moved to DuPont, thence to Osgood and on the 14th of July to Sunman's station. It returned to Indianapolis on July 17th and was mustered out.
James Dickerson Harmon was born 8 Jan 1828 - some old family letters refer to him as "Jay". It is possible he served as well, but more than one James Harmon was in the Union Army and the information available on the Internet has not indicated that any of them enlisted in Boone County where Jay was living at the time of the War.
Nelson S. Harmon was born 5 Jun 1833. He married Catherine Wilson, 19 Jun 1853 in Boone County, and had three children at the beginning of the War. Nelson enlisted in Company L, Indiana 3rd Cavalry Regiment on 23 Oct 1861. He was mustered out of the 3rd Cavalry on 15 Dec 1864 at Savannah, Georgia, and transferred to Company A, Indiana 8th Cavalry Regiment the same day. Nelson was mustered out of the 8th Cavalry Regiment on 20 Jul 1865 at Indianapolis, IN, having served pretty much the entire War. The Indiana Civil War service records have not been filmed so little can be discovered online other than just the most basic information.
Francis Marion Harmon, born 8 Feb 1835, married Minerva Utterback about 1856. By one of those strange genalogical quirks, I am kin to both. Francis was a great, great grand-uncle. Minerva was a 5th cousin, several times removed, her family going back to the ironworkers at the Germanna colony in Virginia. The family had moved to Iowa before the civil War began, living near Minerva's parents, and had at least three children. Francis was wounded in the War, then died of typhoid fever. Letters he wrote to his family just before his death, as well as Minerva's letter informing a brother of his death, have been transcribed on the Utterback GenForum message board.
Francis M. Harmon, whose residence was Glenwood, Iowa, enlisted 10 Oct 1861, as a Private, in Company F, 15th Infantry Regt, Iowa. He gave his age as 26 and was mustered in on 18 Nov 1861. He was severely wounded in the hand on 6 April 1862 at the Battle of Shiloh, Tennessee, and died of typhoid fever at the division hospital on 1 Jun 1862. He is buried at Pittsburg Landing, now Shiloh National Cemetery - a picture of his grave marker is on their website. There were 760 soldiers of the 15th Iowa, of that number there were 185 casualties, killed, wounded, or missing, at Shiloh - nearly a fourth of the regiment.
The youngest son [and youngest child] of James and Philadelphia was Charles, born 25 Dec 1844. The parents both died in 1847 and Charles lived with his older brother Jay. With all those brothers in service, he apparently could not to wait to "join up". The family tradition is that he first enlisted before his 16th birthday, but he should have turned 16 in December of 1860, before the war started. Charles was likely not quite 18 at his first enlistment. Whatever may be the truth of that story, his older brother Jay got him released from that first enlistment in Company L of the 3rd Indiana Cavalry, and took him home. Charles did enlist again 9 Apr 1863, Company A of the 8th Cavalry. His brother Nelson served in both companies as well. Charles was mustered out on 20 Jul 1865 at Indianapolis, along with Nelson. He may also have an invalid pension file that I have not yet ordered from the National Archives - the Index card for Charles Harmon lists both companies.