He offered to employ Mormons to help defend the West.
Explanation:
The "Mormon group" in this question refers to the members of The Church of Jesus Christ of Latter-day Saints who were trying to get help from the government in order to migrate west to the Rocky Mountains and Salt Lake Valley. They were trying to flee religious persecution. After being denied help several times, eventually President James K. Polk agreed to help in exchange of enlisting some members of the church in order to fight in the Mexican-American war. This is known as the "Mormon Batallion."
