Sen. Angus King came to the floor Wednesday afternoon to discuss next week’s 150th anniversary of the Battle of Gettysburg, literally sketching out a battle map.

“At the Battle of Gettysburg, Mr. President, the Southern army came in from the North and the Northern army came in from the South,” the Maine independent noted. “They met almost by accident in this town.”

King used an easel and an over-sized pad of paper to sketch out the events at Gettysburg involving Joshua Lawrence Chamberlain, who had been a student and later a professor at Bowdoin College, a small liberal arts institution in Maine where King had served as a lecturer.

Chamberlain was the colonel of the 20th Maine regiment, which was dispatched to secure an unoccupied hill at what King explained was “the extreme left flank of the entire Union Army.” Ordered to hold the ground at what came to be known as Little Round Top at all costs, the 20th Maine faced off against the 15th Alabama.

“By the third and fourth charge it became hand-to-hand combat,” King said. He went on to tell the whole story:

After the war, Chamberlain served as Bowdoin’s president. The college has an online repository of information about Chamberlain’s service, maintained by the George J. Mitchell Department of Special Collections and Archives (named, coincidentally, for the former Senate majority leader).