Complex sentence: By the late 13th century Varangians were mostly ethnically assimilated by Byzantine Greeks, though the guard operated until at least mid- 14th century and in 1400 there were still some people identifying themselves as "Varangians" in Constantinople.
Split into simpler sentences: By the late 13th century Varangians were mostly ethnically assimilated by Byzantine Greeks, though the guard operated until at least mid- 14th century. In 1400 there were still some people identifying themselves as "Varangians" in Constantinople.