The Skeleton Army by Alis Hawkins

Why should the devil have all the best tunes? The Salvation Army has come prancing and singing from the slums of London to the poorest quarters of Oxford, but along with its red hot gospel preaching and music hall songs it brings a prohibition message which sparks immediate opposition and violence.
An Army soldier – an ex-drunk – is brutally killed and a note suggests that the Salvation Army's shadowy enemy, the Skeleton Army, is responsible.
With the police unwilling to come between the two forces, Non Vaughan, aspiring journalist and great hope of the Oxford women's college movement, and Basil Rice, Jesus College fellow and union-sanctioned guardian of the dead man's family, are compelled to investigate.
But as the threats from both sides escalate, resulting in a second death, Non and Basil realise that they must stop the fighting before it results in an outright war. For with the University's annual commemoration week fast approaching, the entire city could be engulfed in fire and blood...
An utterly compelling historical mystery, and a fascinating portrait of Victorian Oxford, perfect for fans of Andrew Taylor, C. J. Sansom and Antonia Hodgson.