[3] During the second day's fighting at Gettysburg on July 2, Chamberlain's regiment occupied the extreme left of the Union lines at Little Round Top.

Chamberlain's men withstood repeated assaults from the 15th Alabama Infantry Regiment and finally drove the Confederates away with a downhill bayonet charge.

Chamberlain was severely wounded while commanding a brigade during the Second Battle of Petersburg in June 1864, and was given what was intended to be a deathbed promotion to brigadier general.

In April 1865, he fought at the Battle of Five Forks and was given the honor of commanding the Union troops at the surrender ceremony for the infantry of Robert E. Lee's Army at Appomattox Court House, Virginia.

Chamberlain's grandfather, Joshua, was a ship builder and colonel during the War of 1812, notably involved at the Battle of Hampden, before moving his family to a Brewer farm in 1817.

In the fall of 1855, Chamberlain returned to Bowdoin, and began a career in education, first as an instructor in logic and natural theology, then as professor of rhetoric and oratory.

On several occasions, Chamberlain spoke freely of his beliefs during his class, urging students to follow their hearts in regards to the war while maintaining that the cause was just.

"[8] Many faculty at Bowdoin did not feel his enthusiasm for various reasons and Chamberlain was subsequently granted a leave of absence (supposedly to study languages for two years in Europe).

[citation needed] The 20th Maine fought at the Battle of Fredericksburg, suffering relatively small numbers of casualties in the assaults on Marye's Heights, but were forced to spend a miserable night on the freezing battlefield among the many wounded from other regiments.

Chamberlain chronicled this night well in his diary and went to great length discussing his having to use bodies of the fallen for shelter and a pillow while listening to the bullets zip into the corpses.

On July 2, the second day of the battle, Union forces were recovering from initial setbacks and hastily regrouping into defensive positions on a line of hills south of the town.

The men from Maine waited until troops from the 15th Alabama Infantry Regiment, commanded by Col. William C. Oates, charged up the hill, attempting to flank the Union position.

With many casualties and ammunition running low, Col. Chamberlain recognized the dire circumstances and ordered his left wing (which was now looking southeast, compared to the rest of the regiment, which was facing west) to initiate a bayonet charge.

The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Colonel Joshua Lawrence Chamberlain, United States Army, for extraordinary heroism on 2 July 1863, while serving with 20th Maine Infantry, in action at Gettysburg, Pennsylvania, for daring heroism and great tenacity in holding his position on the Little Round Top against repeated assaults, and carrying the advance position on the Great Round Top.

Despite the injury, Chamberlain withdrew his sword and stuck it into the ground in order to keep himself upright to dissuade the growing resolve for retreat.

The wound was considered mortal by the division's surgeon, who predicted he would perish; Chamberlain's incorrectly recorded death in battle was reported in the Maine newspapers, and Lt. Gen. Ulysses S. Grant gave Chamberlain a battlefield promotion to the rank of brigadier general after receiving an urgent recommendation on June 19 from corps commander Maj. Gen. Gouverneur K. Warren: "He has been recommended for promotion for gallant and efficient conduct on previous occasion and yesterday led his brigade against the enemy under most destructive fire.

Despite losses, another wound (in the left arm and chest that almost caused amputation), and nearly being captured, Chamberlain was successful and brevetted to the rank of major general by President Abraham Lincoln.

On the morning of April 9, 1865, Chamberlain learned of the desire by General Robert E. Lee to surrender the Army of Northern Virginia when a Confederate staff officer approached him under a flag of truce.

"[13] The next day, Chamberlain was summoned to Union headquarters where Maj. Gen. Charles Griffin informed him that he had been selected to preside over the parade of the Confederate infantry as part of their formal surrender at Appomattox Court House on April 12.

[15]Chamberlain stated that his salute to the Confederate soldiers was unpopular with many Unionists, but he defended his action in his posthumously published 1915 memoir The Passing of the Armies.

During his time in office, he was attacked by those angered by his support for capital punishment and by his refusal to create a special police force to enforce the prohibition of alcohol.

During this time, there were threats of assassination and kidnapping, and on one occasion, he went outside to face down a crowd of 25–30 men intending to kill him, and both sides offered bribes to appoint him a United States senator.

[21][22] Chamberlain served as Surveyor of the Port of Portland, Maine, a federal appointment, and engaged in business activities, including real estate dealings in Florida (1885) and a college of art in New York, as well as hotels.

[citation needed] In 1893, 30 years after the battle that made the 20th Maine famous, Chamberlain was awarded the Medal of Honor for his actions at Gettysburg.

Despite the support of Acting Secretary of War Russell Alger and President William McKinley, he was passed over due to health issues.

[citation needed] In the alternate history 2003 novel Gettysburg: A Novel of the Civil War, written by Forstchen and Newt Gingrich, Chamberlain is featured as a character.

In the book, an alternate history of the Civil War, Chamberlain makes a heroic stand similar to the real life battle on Little Round Top.

Unlike in real life, Chamberlain is overwhelmed, wounded, and forced to surrender, but he survives and returns in the third book of the series, Never Call Retreat (2005).

"[33] Another Forstchen work, "A Hard Day For Mother", is a short story from the first volume in the variety anthology series Alternate Generals edited by Harry Turtledove.

On the Showtime TV series Homeland, the character Nicholas Brody tells his family the story of Chamberlain, encouraging them to emulate him.