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): in 1263 , the chieftans of the eastern part of iceland became the last to pledge their loyalty and obedience to the norwegian king , an event which brought about a more complete end to the icelandic commonwealth and the icelandic civil war.