Complex sentence: The most recent Fort Wingate (1868-1993) was established at the former site of Fort Lyon, on the southern edge of the Navajo territory, initially to control and "protect" the large Navajo tribe to its north.
Split into simpler sentences: The most recent Fort Wingate (1868-1993) was established at the former site of Fort Lyon, on the southern edge of the Navajo territory. The initial purpose of this fort was to control and "protect" the large Navajo tribe to its north.