Eleven days later, troops led by Frémont, who had acted on his own authority, arrived from Sutter's Fort to support the rebels.

Prior to the Mexican–American War, preparations for a possible conflict led to the U.S. Pacific Squadron being extensively reinforced until it had roughly half of the ships in the United States Navy.

Commodore John Drake Sloat, commander of the Pacific Squadron, on being informed of an outbreak of hostilities between Mexico and the United States, as well as the Bear Flag Revolt in Sonoma, ordered his naval forces to occupy ports in northern Alta California.

To supplement this remaining force, Commodore Stockton ordered Captain John C. Frémont, on the U.S. Army Corps of Topographical Engineers survey, to secure 100 volunteers in addition to the California Battalion he had organized earlier.

The core of the California Battalion was the approximately 30 army personnel and 30 scouts, guards, ex-fur trappers, Indians, geographers, topographers and cartographers in Frémont's exploration force, which was joined by about 150 Bear Flaggers.

Prior to the U.S. occupation, the population of Spanish and Mexican people in Alta California was approximately 1500 men and 6500 women and children, who were known as Californios.

On August 13, 1846, when Stockton's forces entered Los Angeles with no resistance, the nearly bloodless conquest of California seemed complete.

The force of 36 that Stockton left in Los Angeles was too small, and enforced a tyrannical control over the people of the city.

On September 29, in the Siege of Los Angeles, the independent Californios, led by José María Flores, forced the small American garrison to retire to the harbor.

In late November, General Stephen W. Kearny, with a squadron of 100 dragoons, finally reached the Colorado River at the present-day California border after a grueling march across the province of Santa Fe de Nuevo México and the Sonoran Desert.

21 of Kearny's troops were killed in the botched engagement, the largest number of American casualties in the battles of the California Campaign.

The last significant body of Californios surrendered to American forces on January 12, marking the end of hostilities in Alta California.

Three private merchant ships, Thomas H Perkins, Loo Choo, and Susan Drew, were chartered, and the sloop USS Preble was assigned convoy detail.

Over the next five months, until their discharge on July 16, 1847, in Los Angeles, they trained and performed garrison duties at several locations in southern California.

By the terms of the treaty, Mexico formally ceded Alta California along with its other northern territories east through Texas, receiving US$15,000,000 (equivalent to $528,230,769 in 2023) in exchange.

While we cannot anticipate this result but with painful regret, the inevitable destiny of the race is beyond the power or wisdom of man to avert.