Simplify the following text for a Grade 10 native English-speaking person.
Original: A self-confident Soest from 1444 to 1449 liberated itself from the Bishop of Cologne , who controlled Westphalia ( the so-called Soester Fehde ) .
Simplified: A self-confident Soest from 1444 to 1449 freed itself from the Bishop of Cologne , who controlled Westphalia ( the so-called Soester Fehde ) .