Who is Colonel Joshua Lawrence Chamberlain from The Mostly True Adventures of Homer P. Figg and what is their importance?

Colonel Joshua Lawrence Chamberlain is a real officer of the Union Army who fought at Gettysburg as the commander of the 20th Maine. Chamberlain and his men fought at the top of Little Round Top, charged with keeping the Confederate Army from taking the hill and thus giving them access to the Union's left flank. Chamberlain's men fought hard, but soon ran out of ammunition. Chamberlain ordered his men to fix bayonets and fight hand to hand combat. Chamberlain's men won the charge, forcing the remaining Confederates to surrender. In this novel, Homer and Harold fight alongside Chamberlain during this notorious battle.