Definition: Rewrite each original sentence in order to make it easier to understand by non-native speakers of English. You can do so by replacing complex words with simpler synonyms (i.e. paraphrasing), deleting unimportant information (i.e. compression), and/or splitting a long complex sentence into several simpler ones. The final simplified sentences need to be grammatical, fluent, and retain the main ideas of their original counterparts without altering their meanings.
Input: 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.

In 1263, leaders of east Iceland were the last to give their loyalty to the Norwegian king, bringing end to the Icelandic Commonwealth and Icelandic civil war.