Question: When did Jim Savage lead the Mariposa Battalion in to the west?
About the article "Yosemite National Park", section "Ahwahneechee and the Mariposa Wars".

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Jim Savage or James D. Savage, (1817–1852) was a California pioneer.
He was a 49er, businessman, American soldier in the Mexican American War, and commander of the California Militia, Mariposa Battalion in the Mariposa War, and the discoverer of the Yosemite Valley. 
When local militia failed to quell the uprising of the tribes, the governor of California, John McDougall put Savage at the head of a unit of State Militia called the Mariposa Battalion with the rank of Major.
On March 25, 1851, Savage marched at the head of a company of the Mariposa Battalion which included a Doctor Lafayette Bunnell, who wrote about the expedition.
Marching into the Sierra wilderness, they came upon Yosemite Valley at Inspiration Point and became the first non-indigenous discoverers of Yosemite Valley.
Discovery was not the main purpose of the trip: the Battalion rode out in search of Native American tribal leaders believed to have been involved in recent raids on American settlements.
After campaigns up the rivers into the mountains and taking control of the Yosemite, the tribes submitted to moving to a reservation ending the Mariposa War and the Mariposa Battalion was disbanded. 
Mariposa Battalion was a California State Militia unit formed in 1851 to fight the Yosemites and Chowchillas in the Mariposa War.
After a force under Mariposa County Sheriff James Burney was found unequal to the task of defeating the Indians, Burney made an appeal to Governor John McDougal for help.
This led to authorizing an organization of two hundred men into the Mariposa Battalion.
The Mariposa Battalion was mustered 12 February 1851.
Sheriff Burney was the first choice for the Major to command the unit, but Burney declined due to his other responsibilities in Mariposa.
James D. Savage was then chosen as major, primarily due to his scouting abilities.
The battalion was divided into three companies: Company A commanded by John J. Kuykendall, with seventy men; Company B under John Boling, with seventy-two men; and Company C, under William Dill, with fifty-five men.
Other officers elected included M. B. Lewis as Adjutant, A. Brunson as Surgeon and Vincent Hailor as Guide.
A camp was established two and one-half miles from the town of Mariposa near Savage's Agua Fria trading post. 
Ahwahneechee and the Mariposa Wars.
As revealed by archeological finds, the Yosemite Valley has been inhabited for nearly 3000 years.
The Paiute and Sierra Miwok peoples lived in the area long before the first explorations by American settlers into the region.
A band of Paiute called the "Ahwahneechee" were living in the Yosemite Valley when the first known group of European Americans entered it.
The California Gold Rush in the mid-19th century dramatically increased travel by European-Americans in the area, causing competition for resources between the regional Paiute and Miwok and the miners and hangers on.
In 1851 as part of the Mariposa Wars intended to suppress Native American resistance, United States Army Major Jim Savage led the Mariposa Battalion into the west end of Yosemite Valley.
He was pursuing forces of around 200 Ahwahneechee led by Chief Tenaya.
Accounts from this battalion were the first well-documented reports of ethnic Europeans entering Yosemite Valley.
Attached to Savage's unit was Dr. Lafayette Bunnell, the company physician, who later wrote about his awestruck impressions of the valley in "The Discovery of the Yosemite".
Bunnell is credited with naming Yosemite Valley, based on his interviews with Chief Tenaya.
Bunnell wrote that Chief Tenaya was the founder of the Pai-Ute Colony of Ah-wah-nee.
The Miwok, a neighboring tribe, and most white settlers considered the Ahwahneechee to be especially violent because of their frequent territorial disputes.
The Miwok term for the Pai-Ute band was "yohhe'meti," meaning "they are killers".
Correspondence and articles written by members of the battalion helped to popularize the natural wonders of the Yosemite Valley and the surrounding area.
Chief Tenaya and his Ahwahneechee were eventually captured and their village burned; they were removed to a reservation near Fresno, California.
The chief and some others were later allowed to return to Yosemite Valley.
In the spring of 1852 they attacked a group of eight gold miners, and then moved east to flee law enforcement.
Near Mono Lake, they took refuge with the nearby Mono tribe of Paiute.
They stole horses from their hosts and moved away, but the Mono Paiutes tracked down and killed many of the Ahwahneechee, including Chief Tenaya.
The Mono Paiute took the survivors as captives back to Mono Lake and absorbed them into the Mono Lake Paiute tribe.
A reconstructed "Indian Village of Ahwahnee" has been erected behind the Yosemite Museum, located next to the Yosemite Valley Visitor Center.
Mariposa-Yosemite Airport is a public airport located four miles (6 km) west of the central business district of Mariposa, in Mariposa County, California, United States.
It is owned by the County of Mariposa.
Although most U.S. airports use the same three-letter location identifier for the FAA and IATA, Mariposa-Yosemite Airport is assigned MPI by the FAA but the IATA assigned MPI to Mamitupo, Panama).