Three Hearts and Three Lions by Poul Anderson

A World War II freedom fighter is transported to a medieval realm of magic and myth to undertake a great but perilous quest in this classic fantasy adventure Holger Carlsen is a rational man of science. A Danish engineer working with the Resistance to defeat the Nazis, he'??s wounded during an engagement with the enemy and awakens in an unfamiliar parallel universe where the forces of Law are locked in eternal combat with the forces of Chaos. Against a medieval backdrop, brave knights must take up arms against magical creatures of myth and faerie, battling dragons, trolls, werewolves, and giants. Though Holger has no recollection of this world, he discovers he'??s already well-known throughout the lands, a hero revered as a Champion of Law. He finds weaponry and armor awaiting him'??precisely fitted to his form'??and a shield with three hearts and three lions emblazoned upon it. As he journeys through a realm filled with wonders in search of the key to his past, Holger will call upon the scientific knowledge of his home dimension'??the destinies of both worlds hanging in the balance. Before Thomas Covenant, Roger Zelazny'??s Amber, and J. R. R. Tolkien'??s The Lord of the Rings, the great Poul Anderson introduced readers to the Middle World and the legendary hero Ogier the Dane. Inventive and exciting, Three Hearts and Three Lions is a foray into fantasy that employs touches of science fiction from an award-winning master of the speculative.

This book is part of the "Operation Otherworld" series.
Here are some other books from this series: