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: The battle began a seven-year war which established the Rhine as the boundary of the Roman Empire for the next four hundred years, until the decline of the Roman influence in the West.

The battle began a seven-year war. The war created the Rhine as the boundary of the Roman Empire for the next four hundred years.It lasted until the decline of the Roman influence in the West.