with some joining John Frémont's California Battalion. U.S. conquest of California Prior to the Mexican–American War of 1846–1848, the Californios forced the Mexican appointed governor, Manuel Micheltorena, to flee back to Mexico with most of his troops. Pío Pico, a Californio, was the governor of California during the conflict. The Pacific Squadron, the United States Naval force stationed in the Pacific was instrumental in the capture of Alta California after war was declared on April 24, 1846. The U.S. Navy with its force of 350–400 U.S. Marines and "bluejacket" sailors on board several U.S. Naval ships near California were essentially the only significant United States military force on the Pacific Coast in the early months of the Mexican–American War. The Royal Navy Pacific Station ships in the Pacific had more men and were more heavily armed than the U.S. Navy's Pacific Squadron, but did not have orders to help or hinder the occupation of California. New orders would have taken almost two years to get back to the British ships. The Marines were stationed aboard each ship to assist in ship-to-ship combat, as snipers in the rigging, and to defend against boarders. They could also be detached for use as armed infantry. In addition, there were some "bluejacket" sailors on each ship that could be detached for shore duty as artillery crews and infantry, leaving the ship functional though short handed. The artillery used were often small naval cannon converted to land use. The Pacific Squadron had orders, in the event of war with Mexico, to seize the ports in Mexican California and elsewhere along the Pacific Coast. The only other United States military force in California at the time was a small exploratory expedition led by Lieutenant Colonel John C. Frémont, made up of 30 topographical, surveying, etc. army troops and about 25 men hired as guides and hunters. The Frémont expedition had been dispatched to California, in 1845, from the U.S. Army Corps of Topographical Engineers. Rumors that the Californio government in California was planning to arrest and deport many of the new residents as they had in 1844 led to a degree of uncertainty. On June 14, 1846, thirty-three settlers in Sonoma Valley took preemptive action and captured the small Californio garrison of Sonoma, California without firing a shot and raised a homemade flag with a bear and star (the "Bear Flag") to symbolize their taking control.