'Kearny's March'

In 1846 Gen. Stephen Kearny was ordered to leave Kansas with 2,000 U.S. troops and move west to California. The problem was California was still the property of Mexico, as was much of the "southern route" taken by Kearny's little army. This did not sit well with many Mexicans who also soon found themselves dealing with the U.S. Navy, "Pathfinder John C. Freemont and his small force of mountain men and explorers, Gen. Zachary Taylor's army regulars, Col. Alexander Doniphan's Missouri volunteers, more army regulars under Winfield Scott and a 500-man" Mormon Battalion" on loan from a cash-needy Brigham Young.
Groom incorporates all of this into his book as well as the tragic Donner Party and some early Mormon history.
In a very busy 270-pages Groom also writes about the political machinations of the Polk presidency and the chaotic world that was mid-19th century Mexico.
The book is jam packed with interesting tidbits and encourages further reading on the many subjects it introduces.
It was a momentous time in the history of North America. Th events of 1846-47 left a last impact on both the U.S. (which was doubled in size) and Mexico, which was momentously ill served by its corrupt and incompetent political and military leadership.
"Kearny's March" is a fine read in itself and a springboard to further reading.