Godslayer

From the back cover of the DAW first edition: "Gods' magic, mortal's doom - in a land where magic is real, where elves and dragons menace the unwary, and where the Norse gods wage a deadly campaign, using mortals as their favorite pawns, Loki, god of deception, and Freyr, god of war, are locked in a battle that could tip the universal balance toward order or eternal chaos. Searching the alternate timeways, Freyr has reached out to snatch Al Larson, twentieth-century American soldier from the midst of a firefight in Vietnam, flinging him through time and space into the body of an elvish warrior to stand against Loki and his sorcerous ally Bramin. Torn from a world where bullets and grenades are the weapons of choice, and locked into an elvish body on a world where sword and spell are the means of battle. Al must adapt swiftly - or die. For the gods have marked him as their own private battleground, and Al's only chance rests in completing the quest Freyr has set him, a quest that will lead him to the very gates of Hel, where he must save a god - or destroy one!"