Open this photo in gallery: Hohenzollern Castle, a hilltop palace in Germany’s Zollernalbkreis district, overlooks the countryside of the Swabian Alps.Florian Trykowski/German National Tourist Board Dave Meyrick looked down at the vast valley in the shadow of Hohenzollern Castle, a hilltop palace in Germany’s Zollernalbkreis district. He could see the valley well from the vantage point – and even picture how his German ancestors must have seen it. Meyrick, a veteran, found himself imagining what his forebears might have experienced centuries ago in their own battles: perhaps in this valley, to defend the castle. Before he started to dig into...