Forbes, a contemporary and colleague of Winslow Homer and Thomas Nast, was a battlefield illustrator for Frank Leslie's Illustrated Newspaper during the Civil War. In 1876 he published a portfolio of 40 etchings, Life Studies of the Great Army, showing the reality of Civil War camp life. The edition of these large prints is not known, but experts in the field estimate an edition of no more than 200 images. The etchings were printed on thick wove paper with full margins.

Sanctuary shows the moment when a family of African-Americans has sighted the Union lines and knows that they are safe. It was the last etching in the portfolio, summing up what the war was all about for many.

The New York City native was a student of Arthur Fitzwilliam Tait and exhibited at the National Academy of Design.