Baja California is a Mexican peninsula. It borders the Mexican state of Sonora to the east and the U.S. state of California to the north. A long desert peninsula with few resources and baking sun, it is anchored at the northern end by the city of Tijuana and at the southern end by Cabo San Lucas. It was a single state prior to 1804, when the northern and southern parts were separated.
Following the Confederate purchase of Sonora and Chihuahua in 1881, Baja California was cut off by land from the rest of Mexico and was the only part of Mexico to share a border with US. Due to the subsequent Mexican alliance with the Confederacy in the Great War, as well as its physical isolation from the rest of the Empire, Baja California found itself invaded by the US in 1915. This invasion, indifferently supplied and poorly executed, resulted in many US casualties to the dug-in Mexican Army and their Confederate advisers. The US withdrew to the pre-war border and no territory changed hands at the end of the war.
During the Civil War of the 1920s, many Mexicans fled to the US through Baja, seeking political asylum or simply work in the more prosperous USA. After the Mexicans once again allied with the Confederates during the Second Great War, fighting was slow to begin in the West. The first major blow fell in March 1942, when a US navy task force steamed south from San Diego and bombarded Tijuana to discourage any Mexican or Confederate operations into California.
Baja California was the target of an amphibious invasion by the United States Marine Corps in 1943. The United States seized the peninsula through a combined arms operation involving a simultaneous overland push from California and began naval and air operations against the Confederate west coast in Sonora, restricting the port of Guaymas. While many in the U.S. wondered if the cost have the invasion had been worth it, the C.S. was painfully aware that one more avenue for prosecution of the war had been severed.
At the end of the war, Baja California was the only Mexican territory under US occupation, but the US soldiers there speculated that the US had no intention of retaining the barren, inhospitable piece of land.