Complex sentence: Emperor Tiberius had no intention of giving up the buffer states of the Eastern frontier and sent his nephew and heir Germanicus to the East, who concluded a treaty with Artabanus III, in which he was recognized as king and friend of the Romans.
Split into simpler sentences: Emperor Tiberius had no intention of giving up the buffer states of the Eastern frontier and sent his nephew and heir Germanicus to the East. Germanicus concluded a treaty with Artabanus III, in which he was recognized as king and friend of the Romans.