Why did Oliver Wendell Holmes, Jr. enlist during the American Civil War?

Oliver Wendell Holmes, Jr. enlisted in the American Civil War at the age of 20, driven by a profound conviction regarding the necessity of civic participation. He believed that it is required of a man to share in the passion and action of his time, at the risk of being judged as having never truly lived.1

Reflecting on his service in an 1884 Memorial Day address, Holmes noted that his generation was fortunate to have their hearts "touched with fire" in their youth, allowing them to learn early on that life is a passionate and profound experience. Although he later described the war as an "organized bore" and felt he did nothing remarkable as a soldier, he remained committed to the duty he performed during those three years of service.1