Complex sentence: In the summer of 1853, Walker traveled to Guaymas, seeking a grant from the government of Mexico to create a colony, using the pretext that it would serve as a fortified frontier, protecting US soil from Indian raids.
Split into simpler sentences: In the summer of 1853, Walker traveled to Guaymas, seeking a grant from the government of Mexico to create a colony. He said the colony would serve as a fortified frontier, protecting US soil from Indian raids.