Poul Anderson's "Man Who Counts" aka "War of the Wing-Men" (novel, war, free)

According to Wikipedia, one of the editions of it in book form is a heavily edited one. This post is based on the version that was originally serialized in Astounding.

Story has very colorful setting & environment.

Story summary.

What if, during the creation of Israel during the 1940s, US had sided with Arabs instead of Israel? Neither of these parties is mentioned, of course; it's about a war between two alien nations on their world Diomedes with a party of 3 humans siding with the underdog & giving them major military advantage.

One of the warring side, Drak'ho, is a sea-based nation that has moved into the lands occupied by Lannachska, driving the original inhabitants into interior. Because the fish Drak'ho depends on for survival has inexplicably moved into waters of these shores.

Story has its warts, like brief infodumps in the middle of something interesting or at the beginning of a chapter. And the humor of Van Rijn, one of the 3 humans, didn't always work for me. But it's a fast moving action adventure that I often found difficult to put down.

Fact sheet.

First published: Astounding, February/March/April 1958 as a 3-part serial.
Download full text as part of the scans of 3 issues of Astounding (British edition) where it was serialized in 3 parts: May/June/July 1958.
Rating: A.
Among the stories from Astounding/Analog issues edited by John Campbell.
Related: Stories of Poul Anderson.