After the signing of the Treaty of Guadalupe Hidalgo at the close of the Mexican War, the U.S. acquired much of the present southwestern states. But aside from Hispanic presence in New Mexico, the interior west still belonged largely to the indigenous people who had occupied it for centuries.

The California and Colorado gold rushes drew settlers from eastern states in the 1850s and 1860s. Unlike the trappers and traders of the previous generation, these newcomers exploited land, game, timber, and mineral resources, propelling conflict with Native tribes.

With the coming of the Civil War, the fate of the Southwest hung in the balance. The Confederacy dreamed of expanding to the Pacific coast. Troops from Texas led the initiative. Pivotal battles took place in southern Arizona and throughout New Mexico.

Union regiments marched from distant California and Colorado to prevent the Confederate takeover. But it wasn’t a simple matter of Union vs. Confederate. The Apache, Comanche, Navajo, and other tribes were still determined to retain their own rights to their territories and ways of life.

In The Three-Cornered War, Nelson builds a chronological narrative of the war for the Southwest through the stories of nine individuals representing the trilogy of interests. Some served prominent military or government roles. Most will be new to readers, including ordinary soldiers, a Navajo weaver, and an Army wife.

Nelson incorporates official records, personal diaries and letters, memoirs and maps, to give the reader an intimate sense of the motivations and actions taken by the featured individuals. She weaves their stories in a way that demonstrates how each became part of the tide of events.

Though this aspect of the Civil War has been largely under the radar to most Americans, The Three-Cornered War illustrates just how crucial the Union victory for the Southwest was for the fate of the nation, and how devastating the outcome for Native Americans.