Simplify the following text for a Grade 8 native English-speaking person.
Original: When a commune was formed , all participating members gathered and swore an oath in a public ceremony , promising to defend each other in times of trouble , and to maintain the peace within the city proper .
Simplified: When a commune was formed , all particpitating members gathered and swore an oath together , in public , they would defend each other in time of trouble . In addition they would swear to maintain the peace within the city proper .