Complex sentence: When the Spaniards arrived in Cerquin, Lempira was fighting against neighboring chiefs, but because of their threat, he allied with the Lenca subgroup of Cares thus unifying the different Lenca tribes.
Split into simpler sentences: When the Spaniards arrived in Cerquin, Lempira was fighting against neighboring chiefs. Because of the Spanish threat, he allied with the Lenca subgroup of Cares and unified the different Lenca tribes.