High ranking officers of the Mexican Expeditionary Guard oversee a secured beach head in Baja California, (The lower half of the California Republic's territory in Shattered America), as land forces rally to begin the push deeper inland. In the years 1910-1918, 60 years after the cataclysmic event known as "The Split,"where the fledgling United States had fallen apart into three separate countries (Union, Confederates, and California), the newfound California Republic took advantage of the revolutionary chaos occurring in Mexico at the time to expand it's borders, taking the opportunity to annex the land mass of Baja California. After the revolutionary forces in Mexico were crushed by the Diaz Regime, there had been a number of attempts to retake the land from California over the years that failed each time.
Now 100 years later, shortly after the outbreak of the Second American Civil War, fighting initially began with the Americans and Confederates to the east of North America. The California Republic to the west condemned the Confederacy, and made preparations to intervene on the Union's behalf. However as the Union was distracted with the Confederacy, Mexico enters it's hand in the Second American Civil War by launching a sudden mass invasion of Baja California across the Sea of Cortez, opening a new front of the war to the south-west. This blocked California's attempt to aid the Union from the west, as part of Mexico's deal in The Trans-Atlantic Alliance's war plans. Mexico used the war as an opportunity to settle a personal beef that lasted over 100 years with the California Republic, and Baja California is overwhelmed and reconquered by Mexico in less than a year.