The read is brisk (191 pages), but is highly informative and gives a sense of just how tumultuous Mexico was in the 1st half of the 19th century. It's almost as if the whirlwind nature of Henderson's presentation fits in with the whirlwind of Mexican society and politics of the period.
The final analysis of Henderson's analysis is that any Mexican-American War was destined to be an American victory, but the war itself was not an inevitability. What fostered the conflict was a combination of factors and personalities that feasted on popular ethos present in both the U.S. and Mexico.
The Mexico of the 19th century seemed beyond redemption for the bellicose Manifest Destiny proponents who viewed the whole country as inferior. Most were satisfied to strip it of the sparsely populated northern territories, while a select view advocated total annexation and then some form of violent exploitation.
Sadly, Mexico itself was riven by racial and social conflict. Dating back to its Spanish colonial days, those of increasingly white stock were believed to be best able to govern and indeed held most of the power and wealth. The country's population remained majority Indian and these persons remained desperately poor and powerless in the political system. Mestizos were the 2nd largest group and held modest wealth and power, but their clamoring for greater rights would lead to Mexico breaking down into two basic camps (with several cleavages amongst them).
The federalists were generally in favor of mimicking the political and economic ideas of the United States. Their belief was that their own vast and diverse (and also poorly connected physically) country could not survive unless each region was bequeathed with rights and responsibilities to enjoy. Centralist, however, were alarmed at any prospect of spreading power to the Mexican states, and by extension the poorer and browner peoples that lived there. They preferred that power be exercised from Mexico City by a cabal of wealthy elites, possibly under the aegis of some imported European monarchy.
Over the years, a startling array of constitutions, governments, presidents, dictators and rebellions rocked Mexico as the country attempted to find some cohesion. All of this precipitated the growing fear that the country would never catch up with the economically expanding United States that was beginning to spread its tentacles across the continent. The only semblance of a unifying force to be found in Mexico was opposition to U.S. expansion.
The flashpoint would be Texas. The sparsely inhabited territory was the most obvious target of American expansion (some Americans claiming it was apart of the Louisiana Purchase of 1803). Mexico's only hope was to bolster the population of barely 6,000 with migrants. Unfortunately for Mexico, none of its people wanted to (or could) move to such a volatile location. It was remote from the heart of the country and travel there was arduous. Attempts to attract European immigrants also failed. The only people intrigued with migrating to Texas were Americans.
Mexico could either attempt to totally deny all immigration (nearly impossible) or try to manage the stream by land grants and maybe engender some loyalty amongst the Anglos. Initially, the latter plan was a modest success, but eventually it brewed trouble as more and more Americans settled and became more and more restive under what they saw as incompetent Mexican rule. Some of the gripes were legitimate (concerning poor governance and bureaucracy) while the big bugbear was wholly illegitimate (whining over Mexico's anti-slavery laws).
Texas's ensuing revolt and independence rocked Mexico and was a thorn in the nation's pride. It became an object of obsession to retake the area. No Mexican politician could take a conciliatory tone on the issue without quickly falling out of favor. In the face of its glaring national weakness, Mexicans could not bring themselves to let Texas go despite the clear indications it was lost forever.
The Texans for their part poked at the sore Mexican wound by insisting their boundary was the Rio Grande and not the Nueces River which it had been ever since Spanish colonial rule. This would become the pretext for American President James Polk's instigation of war in 1846.
But before that charade, Mexico had let it be known quite forcefully to the United States that annexation of Texas would lead to war. Many Americans took the warnings to heart and opposed annexing the territory so as to avoid war, but also to preclude what some saw as an aggressive expansion by slave owners. After sly political maneuvering and outright lies by Polk, the resolution to annex Texas barely squeezed through Congress. The war now became inevitable. And Mexico inevitably lost as its out-of-date army was routed time and again. The elites eventually preferred to lose 55% of the nation's territory instead of prolonging the war and seeing the ensuing empowerment of the country's rabble as guerrilla warriors. They had made a good enough show of national pride.
Still, the war's outcome plunged Mexico into even deeper crises that would leave it ripe for invasion by France in the 1860s. At that same time, the United States suffered its comeuppance for turning the war over settling Texas' self-proclaimed, grandiose boundary into one of naked conquest. The Civil War was catalyzed by the increasingly vitriolic debate over slavery expansion.
As Henderson notes in the conclusion, any sane Mexican realized that they were doomed from the beginning in this conflict with the U.S., but pride prevented rationality from prevailing. It was preferable to suffer a glorious defeat than an ignoble peace.