Task: Text Simplification
Input (English): 1263 - the chieftains of the eastern part of iceland become the last to pledge fealty to the norwegian king , bringing a more complete end to the icelandic commonwealth and the icelandic civil war.
Output (English): 1263 - the chieftains -lrb- the leaders of people or clans -rrb- of the eastern part of iceland become the last to vow fealty -lrb- a feudal tenant 's or vassal 's sworn loyalty to a lord -rrb- to the norwegian king , bringing a more complete end to the icelandic commonwealth and the icelandic civil war.