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.

A seven-year war made the Rhine the edge of the Roman Empire for the next four hundred years, until the decline of the Roman influence.