Simplify the following text for a Grade 9 native English-speaking person.
Original: Huntsville has been important in developing space technology since the 1950s , when the German scientists headed by Dr. Wernher von Braun , brought to the United States at the end of World War II through Operation Paperclip , arrived to develop rocketry for the U.S. Army .
Simplified: Huntsville has been important in developing space technology . Since the 1950s , when the German scientists headed by Wernher von Braun , brought to the United States at the end of World War II through Operation Paperclip , managed to develop rockets for the U.S. Army .