Forward, You Witnesses was authored by Erich Frost. From the United States Holucost Museum:
Musician Erich Frost was a devout Jehovah's Witness active in the religious resistance to Hitler's authority. Frost was caught smuggling pamphlets from Switzerland to Germany and was deported to the Sachsenhausen concentration camp near Berlin. There, he composed this song in 1942. Frost survived the war and died in 1987. This translation is taken from the Jehovah's Witness Songbook.
Simone Arnold Liebster, who sings the English version of the song, was born in 1930 in Mulhouse, French Alsace. After the incorporation of Alsace into the German Reich during World War II, Liebster's family suffered increasing harrassment from the Nazis for following the Jehovah's Witness faith. Eventually both her father (Adolphe Arnold) and mother were arrested and sent to concentration and detention camps while she was placed in a correctional institution for "nonconformist" youth. Liebster has published an autobiography, Facing the Lion: Memoirs of a Young Girl in Nazi Europe
Link to page with an original vocal recording: http://www.ushmm.org/wlc/en/media_so.php?MediaId=3941