In context, the song is sung after the death of the main character to give courage to his pregnant widow, and is sung in a later scene to encourage a graduation class of which his daughter is a member. As a result, it has become a standard, sung by graduation classes in the USA.
In the UK, the song was recorded in the early 1960s by Liverpool group, Gerry and the Pacemakers, and reached number one in the pop charts. It was adopted by Liverpool F.C football supporters, and is now invariably sung by them at matches, and has spread to other football crowds, such as Ajax Amsterdam.