Simplify the following text for a Grade 11 native English-speaking person.
Original: It was almost always accompanied by one or more attached units of auxiliaries , who were not Roman citizens and provided cavalry , ranged troops and skirmishers to complement the legion 's heavy infantry .
Simplified: It was usually accompanied by attached units of auxiliaries , who were not Roman citizens . They provided cavalry , ranged troops and skirmishers to complement the legion 's heavy infantry .