Complex sentence: As a military campaigner, Emperor Wu led Han China through its greatest expansion--at its height, the Empire's borders spanned from modern Kyrgyzstan in the west, to Korea in the east, and to northern Vietnam in the south.
Split into simpler sentences: As a military campaigner, Emperor Wu led Han China through its greatest expansion. At its height, the Empire's borders spanned from modern Kyrgyzstan in the west, to Korea in the east, and to northern Vietnam in the south.