WASHINGTON – Sen. Angus King became Prof. King Wednesday afternoon when he offered his Senate colleagues a history lesson on the Battle of Gettysburg and the role that Maine men played in “probably the defining event in the history of this country.”

Armed with an easel and markers of various colors, King literally sketched out the positions of Union and Confederate troops on the first major day of battle on July 2, 1863 -- exactly 150 years ago next Tuesday.

Not surprisingly, much of King’s speech focused on the role played by the 20th Maine regiment and Col. Joshua Lawrence Chamberlain, a man who, like King, taught at Bowdoin College and would later serve as Maine’s governor.

The regiment of 350-some Mainers were positioned on the far-left end of the Union Army’s line. During fierce fighting on Little Round Top, the regiment repelled several charges by a much-larger Confederate force attempting to flank the Union lines.

Almost out of ammunition and facing another charge, Chamberlain ordered his troops to fix bayonets and to charge the attacking Alabamans.

“There’s a dispute in history whether he also said `charge’ and what his actual order was, but everybody agrees that he uttered the word `bayonets,’” King said. “And his soldiers knew what that meant. And down the hill into the face of the final Confederate charge came 200 crazy guys from Maine.”

The tactic worked, preventing a flanking maneuver that would have subjected Union forces to attacks from both sides. Union troops defeated Confederate forces in a massive battle the following day in what is often described as the turning point of the Civil War.

“I tell this story because it’s a story of our country and it’s a story of how a single person’s actions and bravery can have enormous impact,” King said. “Historians argue about whether this was really the key turning point, was there something else, was there some other regiment at another place. An argument can be made that this college professor from Maine saved the United States.”