The grainy, sepia photograph shows two men, an Australian and a New Zealander. Sydney dock worker Jack Franklyn is partly obscured by bush, leaning forward, his rifle poised and ready. New Zealander Bert Bryan, bare-chested and wearing a beret, crouches at the edge of a trench while shooting at the enemy. They’re in Spain, the battle of Ebro in 1938, and the fact they are fighting together in one of the Spanish civil war’s most seminal and bloody battles lends a gritty new dimension to the revered legend of Anzac. The photograph was recently discovered among personal mementoes in the...