It became the unofficial marching song of the Union Army.

这首歌成为了联邦军中的非官方行军曲。

She heard them singing. They sang a marching song she knew. It was a song about John Brown, an activist against slavery.

她听到他们在歌唱，唱着那一首她听过的行军曲。这是一首关于活动家约翰·布朗反对奴隶制的歌曲。