Operation Chaos

Poul Anderson published Operation Chaos in 1971, and it is a fix-up: the chapters were written as separate stories and gathered into a book. A sequel, Operation Luna, followed in 1999.

Its world is one where science has proved that God exists, and where magic has been turned into a practical technology, mostly by degaussing cold iron. In this version of the mid-twentieth century the United States is at war, and the enemy this time is not Germany: a resurgent Islamic Caliphate has invaded American soil.

Steven Matuchek, a werewolf, and Virginia Graylock, a witch, meet while they are both on a mission to keep the invaders from deploying a secret weapon: a genie let out of a bottle that King Solomon had sealed. They deal with the demon, and in the course of it fall in love. After the war they carry on together, and the later chapters follow their further adventures, including a spell summoned as a student prank that gets out of hand and a honeymoon that brings them up against something considerably worse.