The central government in Mexico City cancelled an attempt to reassert authority and grudgingly recognized the regime of the succeeding Californio governor, Pio Pico, who remained nominally in charge in Alta California.

[1]: 13 The main forces available to the United States in California were the about 400–500 bluejacket sailors and U.S. Marines on board the five ships of the Navy's Pacific Squadron.

In November 1845, Commodore John D. Sloat, commander of the Pacific Squadron, then at Mazatlán, Mexico, was joined by the USS Cyane, which carried orders that if Sloat learned "beyond a doubt" that war between the U.S. and Mexico had begun, he was to seize San Francisco Bay and blockade the other California ports.

John B. Montgomery of the Portsmouth in San Francisco Bay reporting the events of the Bear Flag Revolt in Sonoma and its open support by Brevet Capt.

In a message to Montgomery, Sloat relayed his decision to seize Monterey and ordered the commander to take possession of Yerba Buena (modern-day San Francisco), adding, "I am very anxious to know if Captain Frémont will cooperate with us.

William Mervine of the Cyane came ashore with a small party from the Savannah at 7:30 a.m., seeking the surrender of the port from the Mexican commandant, Capt.

[1]: 171 Captain Montgomery of the Portsmouth received Sloat's message to seize Yerba Buena on 8 July and sent Lt. Joseph W. Revere to Sonoma and Sutter's Fort to notify Fremont of the capture of Monterey.

[1]: 172  Montgomery then sent Purser James H. Watmough to notify Fremont of the occupation of Yerba Buena and Sloat's request for a meeting.

[2]: 149–151  On 23 July, Frémont was appointed major in command of the California Battalion,[7][8] which he had helped form with his 60-man exploratory force and volunteers from the Bear Flag Republic.

[1]: 173  The California Battalion, which varied from 160 to 428 men,[9][4]: 253  drew regular army wages and were used to garrison and maintain order in the towns that had surrendered.