Who wrote the tune for the hymn "Onward, Christian Soldiers"?

Sir Arthur Seymour Sullivan (13 May 1842 – 22 November 1900) was an English composer. He is best known for 14 operatic collaborations with the dramatist W. S. Gilbert, including "H.M.S. Pinafore", "The Pirates of Penzance" and "The Mikado". His works include 24 operas, 11 major orchestral works, ten choral works and oratorios, two ballets, incidental music to several plays, and numerous church pieces, songs, and piano and chamber pieces. His hymns and songs include "Onward, Christian Soldiers" and "The Lost Chord".

"Onward, Christian Soldiers" is a 19th-century English hymn. The words were written by Sabine Baring-Gould in 1865. The Salvation Army adopted the hymn as its favoured processional. The piece became Sullivan's most popular hymn. The hymn's theme is taken from references in the New Testament to the Christian being a soldier for Christ, for example, II Timothy 2:3 (KJV): "Thou, therefore, endure hardness, as a good soldier of Jesus Christ."