Virginia collector Tom Liljenquist has donated nearly 700 photographs from the US Civil War to the Library of Congress. Library curators say the photos are an invaluable depiction of the ordinary men who fought the war.

The war began in 1861 after 11 slave states in the American South seceded from the US, forming the Confederate States of America. More than three million Americans fought in the war.

The Confederate states objected to efforts by the federal government in Washington to restrict the expansion of slavery.

"You can just learn so much about what these guys were carrying, what they were wearing, what their faces looked like," Library of Congress photography curator Carol Johnson told the BBC.

The photographs bring to mind images of US troops who died in Iraq and Afghanistan, Ms Johnson said. An estimated 620,000 died in the Civil War, making it likely many of the subjects did not survive to the war's end.

The collection includes images of the women and children left behind. This unidentified girl in a mourning dress holds a framed photograph of her father, a cavalryman.

The collection, which Mr Liljenquist amassed over 15 years, includes rare photographs of African-American soldiers, like this man and his family. By the war's end more than 180,000 black men had enlisted in the Union army - 85% of those eligible.

Many of the servicemen are strikingly young, barely out of boyhood. Some of the photographs were taken in local studios before the soldiers were deployed to the front lines - and before they had experienced the bloody horrors of the conflict.

However, "some people definitely look like they've seen action, when you look in their eyes," Ms Johnson said.

Some photographers set up shop outside military camps to take souvenir shots of the troops at war.

"We looked for compelling faces that seemed to be saying something across time to us," Mr Liljenquist told the Washington Post.