Note: This entry seemed apropos considering the wounds he received at Williamsburg. The majority of the information in this article comes from Armstrong’s obituary in the November 25, 1863 edition of the Presbyterian banner, on page 3. The facts from his military career I have been able to confirm through the regimental muster rolls. I haven’t been so fortunate with his pre-war life, but it doesn’t read as something exaggerated. Armstrong’s obituary was written by an unidentified friend from college. Thanks once again to Patty Millich, who keeps finding these gems in dusty, out of the way places.
Martin Armstrong was born in Chester County, Pennsylvania in 1828. He was a successful school teacher in Chester and Lancaster counties for several years. Acceding to his mother’s dying wish that he become a minister, he attended Pennsylvania College at Gettysburg (now Gettysburg College) and graduated in 1856.
After graduation, Martin taught for two years at Dr. Foote’s Academy in Romney, Virginia. He then moved to Elizabethtown, Kentucky, where he taught at a large classical school. Armstrong also briefly served as a family tutor in Louisiana before entering Western Theological Seminary in 1860.
Martin left the seminary in October 1861 to enlist as a private in the 6th U.S. Cavalry, where he was assigned to Company M. He participated in the regiment’s training through the winter of 1861, and was promoted to sergeant before it moved to the peninsula.
Sergeant Armstrong was severely wounded in the skirmish at Williamsburg on May 4, 1862, and didn’t return to the regiment until the following June. He rejoined the 6th Cavalry just after Brandy Station at the beginning of the Gettysburg campaign. At the battle of Fairfield on July 3rd, he was one of many 6th U.S. Cavalry troopers who were captured and sent to Belle Isle prison in Richmond.
Armstrong was fortunate enough to be exchanged relatively quickly and brought to Camp Parole near Annapolis, Maryland. He was sent to the U.S. Army General Hospital in Annapolis on September 20th, complaining of pain from his old wound and a severe chill. This turned out to be the onset of typhoid fever, and his body’s ability to resist it had been seriously depleted by his imprisonment. He began to sink rapidly by October 2nd, and died on the morning of October 4, 1863. As with many of those who perished in this hospital or the nearby Camp Parole, he was buried at Ash Grove Cemetery, which was later renamed Annapolis National Cemetery.
Sources:
Obituary, Presbyterian Banner, November 25, 1863, page 3.
Muster Rolls, 6th U.S. Cavalry, M744, NARA
Regular Cavalry in the Civil War 
SGT Martin Armstrong was the regiment's 4th Sergeant-Major, being appointed the position from 01OCT-01DEC1862 while the regiment was camped at Falmouth. Additionally he suffered from injuries at Williamsburg & Fairfield.
He was indeed wounded a second time at Fairfield, receiving a saber wound to the head, according to Broadfooot’s The Medical and Surgical History of the Civil War. I have no record of him as one of the regiment’s sergeants major, however, particularly since he was reportedly absent from the regiment during the period mentioned because of his wounds. Do you have a source for this information? I’ve had some difficulties putting the sergeants major in order, though I’ve identified several. Most ended up with commissions when officers in the regiment ran low.