'How goes the battle?' was a jocular greeting in Canada in the 1940s. 'How's battle?' - without the 'the' - was used by some here from the mid-1930s to mean the battle of life. It's just a variant of 'How's it going?', really, the 'it' meaning life in general.
Sorry, I should have added above that 'How goes the war?' seems to be another variant, though I suppose it might have appeared in the past in literature somewhere, given that 'How goes' is rather an archaic mode of expression.