Simplify the following text for a Grade 6 native English-speaking person.
Original: Hummer was first made by AM General who also made vehicles used by the United States Army . The design of the Hummer H1 is based on the military High Mobility Multipurpose Wheeled Vehicle ( HMMWV â `` Humvee ) .
Simplified: The first vehicle in the Hummer range was the Hummer H1 , based on the Humvee .