Inkbinder's War. Inkbinder's Trilogy, #1

When war erupts across the globe, it does not come alone. Jack Callahan has spent his life hiding what he is- an Inkbinder, capable of weaving magic through hand-crafted cards. But when the attack on Pearl Harbor pulls the United States into the war, hiding is no longer an option. Impersonating his grandfather, Jack joins the Allied Occult Division, a covert unit tasked with combating the supernatural forces shaping the battlefield from the shadows.
There, he's forced into close quarters with soldiers unlike any he's known-among them Alastair Morgan, a disciplined British operative whose presence begins to unsettle Jack in ways he doesn't fully understand. As the Nachtarmee - a secret faction manipulating the Axis through dark, ritual magic - moves to tip the balance of the war, Jack must learn to wield a power he was never meant to carry. But magic is unpredictable, alliances are fragile, and the line between weapon and wielder begins to blur. Because some battles aren't fought on the front lines....