Read: Records reveal the unusual connection between Biden and Lincoln

Zoom in: Biden's forefather, Moses J. Robinette, was a civilian veterinary surgeon in the Union Army during the Civil War, per the Post.

• The records reveal that in March 1864, Robinette got into a fight with another Union civilian employee, John J. Alexander, in a mess tent in Virginia, and ended up cutting Alexander with a knife. Robinette argued that he was acting in self defense, per the Post.
• Still, Robinette was charged with "conduct prejudicial to good order and military discipline," as well as "assault, with attempt to kill," the records reveal. He was convicted on all charges except "attempt to kill."
• He was sentenced to two years' hard labor and incarcerated on the Dry Tortuga Islands off the coast of Florida, at Fort Jefferson — a military prison described by Lincoln's opponents as "American Siberia," the Post reported.

Of note: Robinette's eldest surviving son and Biden's great grandfather, George Hamilton Robinette, remained in West Virginia after 1861, providing a link to Biden's family background in Maryland, Gerleman told Axios in an email.

The intrigue: Three Union Army officers appealed Robinette's sentence directly to Lincoln in July 1864, arguing it was too harsh and that Robinette had been acting in "the excitement of the moment."

• Lincoln ultimately agreed. "Pardon for unexecuted part of punishment. A. Lincoln. Sep. 1. 1864," he wrote in a missive.
• Robinette was freed on special orders from the War Department on Sept. 6, 1864.
• The White House did not immediately respond to Axios' request for comment about whether Biden knows his ancestor's story.

Read the records in full, via DocumentCloud:

Editor's note: This story has been updated with more details.