Simplify the following text for a Grade 11 native English-speaking person.
Original: The so-called Two Plus Four Treaty , signed by the two German states and the four wartime allies , paved the way for German reunification and an end to the western occupation of West Berlin .
Simplified: The Two Plus Four Treaty , signed by the two German states and the four wartime allies , paved the way for German reunification and an end to the western occupation of West Berlin .