Complex sentence: After moving to Tennessee, he spent time with the Cherokee Nation (into which he later was adopted as a citizen and into which he married), performed military service during the War of 1812, and successfully participated in Tennessee politics.
Split into simpler sentences: After moving to Tennessee, he spent time with the Cherokee Nation, into which he later was adopted as a citizen and into which he married. He performed military service during the War of 1812 and successfully participated in Tennessee politics.