On May 29th 1841 the United States of America declared war upon the dictatorial Mexican Empire, which at the time was helping the United States of Central America battle rebels. Taylor, his dragoons and infantry swept into northern California while Scott took his into Utah, assualting entrenched positions in Slat Lake City, while the uncommonly young Redding marched on San Antonio with the main striking force of 6 divisions. Several divisions of both infantry and struck into the other provinces of Texas and New Mexico. All in all 18 divisions were on the march, with more to come, the recruitng stationds were swamped with young men eager to fulfill the nation's manifest destiny.
The war in the west was fluid moving back and forth across the border as Scott was repulsed and Taylor outflanked, yet within two and a half years the coast of california north of Los Angeles had fallen to Taylor and he was working on pacifying that states interior.
Scott with 32,000 had at great cost hammered his way through Utah and taken northern Arizona and eastern Nevada. The harsh deserts of New Mexico were ignored by both parties and the small US forces trying to take controll of them slowly withered away, only bringing the northern third of the state under their controll in that time.
Redding however was unstoppable, San Antonio, Monteray, and everywhere in a straigt line between the Rio Grande and Mexico city fell before his 62,000 vetrans. The Mexicans were numerous but were unable to concentrate more then 20,000 men at any one point and were defeated time and again. There were repeated attempts by both partisans and regular forces to cut Reddings supply lines but they were delt with by a dragoon divsion tasked with that assignment.
Redding laid siege to Mexico City onSeptemberr 6th 1843, gaind control of it and all the surrounding lands by the 15th, and a good thing too for a Mexican army more than 30,000 strong freed up from the fighting in central America which had ended attacked. By this time Reddings arm was down to 45,000 and reinforces had just been redirected to the western theater and none would soon be forth coming. However, weary though they were, they were still to much for the Mexicans throwing them back to regroup again. A fresh 30,000 were thrown against them, it seemed there would be a bitter war of attrition over the Mexican capital as each gave as good as they got and as the fighting dragged into January the outcome of the battle was in doubt.
Yet the Mexican capital had been occupied for nearly five months and was being leveled by constant battle while the country as a whole strained to hold back the growing tide of American advances, therefore on January 9th 1844 Mexico agreed to peace on America's terms. They ceded the provinces of Corpus Criste, San Antonio, El Paso, Santa Fe,Tuba City, Salt Lake City, Moab, Beaver in Utah, Elko on Nevada, Alturus and Eureka. Thus making complete Texas, ceding the entire state of Utah, and the northern reaches of Arizona, New Mexico and California along with eastern Nevada.
Yet the fortunes of the Union were to increase, Mexico had been so economicly devestated by the war that it's people were rioting in the streets for bread and less then year after the treaty was signed on January 4th 1845, Mexico was forced to offer for sale the rest of New Mexico and Arizona to the Union, land so many Mexicans fell bravely defending, for 200,000 in British Sterling. Securing that much British currency was not cheap and combined with the debts incured in the war will weigh heavily on the economy for many years to come, yet with so much new land comming into the Union who can say it was not worth it. Still the defennse budgets, and domestic spending will have to be slashed.
While war raged across the soutwest it sputtered in the rest of the world. Russia ended the war with the Ottomans, rather mercifully only taken four provinces, and after spending years on the defensive Prussia managed to recapture it's western lands from the French and force a white peace. The only large war still going is that between the British Empire and China.
A border dispute in Maine with the British nearly flared into war in April of '44 but the nation was not ready for it so soon after the Mexican war. For now the nation must concentrated on expanding it's economy, although a colonial expidition against British claims in Saskatchawan and British Columbia with Dragoons left over from the war may be entertained. The British themselves had disregarded our singal claim in Alberta and claimed the entire colony. Such interfernece in one of our spheres of influence must not be tolerated, yet the nation must prepared for any attempts of revenge by the Mexicans and be ready to take advantage of such foolishness by driving them out of the rest of California and Nevada, and claiming them has our own.