Vogler, a gaunt ghost with a shrapnel-scarred face, met them at the entrance. "No torches after the first hundred meters," he whispered. "The enemy has listening posts above. We move by touch. And we move fast. If we stop, we die."

The Battle of Pico del Águila became legend. In the International Brigades, they called it La Carga Fantasma —the Ghost Charge. But among the Spanish veterans, it had another name: La Guerra de Jo Que —Jo’s War.

Then, on a rain-choked dawn, Jo Que Guerra received a courier. The message was a single sheet of onionskin paper, stamped with a faded eagle. It was from a German defector named Hauptmann Erich Vogler, a former Sturmtruppen officer who had fled the Nazis and was now fighting for the Republic as an advisor.