In this task, you're given a sentence and your task is to generate a simplified sentence that focuses on lexical paraphrasing from the original sentence given in the input.

in return , rollo swore fealty to charles , converted to christianity , and undertook to defend the northern region of france against the incursions of other viking groups.
rollo converted to christianity and defended the northern region of france against attacks from viking groups because he was loyal to charles.