Have you come across Karl Dallas's book 'The Cruel Wars' - 100 Soldiers' Songs from Agincourt to Ulster? If there's any particular period/aspect perhaps I could direct you to a title in the thread or forward something appropiate. Personally, two of my favourites are not 'traditional' at all but by the late (great) Keith Marsden, set in W.W.2 - 'St. Aubin sur Mer' and, more humourously, 'Left, Left, ,Steady Man'