The Four Stragglers, by Frank L. Packard (epub/Kindle/pdf)
The Four Stragglers opens in the darkness of an unnamed battlefield during the Great War. Cut off from their respective units, three soldiers take refuge in a thicket; a fourth lies dead or unconscious a few metres away. Flares flying above reveal faces, and the cognizant come to recognize that they'd all played parts in a daring jewel heist not two years earlier.