Simplify the following text for a Grade 14 native English-speaking person.
Original: In 1628 the Valais became a republic , the RÃ publique des Sept Dizains \/ Republik der Sieben Zehenden but the bishop remained in power until Napoleon 's troops invaded the Valais and created the RÃ publique du Valais on March 16 , 1798 but on May 1 , 1798 , the Valais became part of the Helvetic Republic and became independent again in 1802 as the Rhodanic Republic .
Simplified: In 1628 the Valais became a republic , the RÃ publique des Sept Dizains\/Republik der Sieben Zehenden under the guidance of the prince-bishop of Sion and the bailli . The bishop remained in power until 1798 when Napoleon 's troops invaded the Valais and declared a Revolutionary RÃ publique du Valais ( March 16 ) which was swiftly incorporated ( May 1 ) into the Helvetic Republic until 1802 when it became the separate Rhodanic Republic .