In this book, Henderson undertakes the task of explaining why Mexico went to war with the United States in 1846, and why that war went so badly for Mexico. He describes the bulk of the English-language work on the war as too focused on military campaigns from the U.S. perspective. Henderson rejects claims that Mexico went to war out of some delusional arrogance. Rather, his thesis is that Mexico entered the war because it was weak, and its leaders knew it.