Simplify the following text for a Grade 15 native English-speaking person.
Original: Early in 188 , Cleander disposed of the current praetorian prefect , Atilius Aebutianus , and himself took over supreme command of the Praetorians at the new rank of a pugione ( `` dagger-bearer '' ) with two praetorian prefects subordinate to him .
Simplified: Early in 188 , Cleander disposed of the current praetorian prefect , and himself took over supreme command of the Praetorians at the new rank of a pugione ( `` dagger-bearer '' ) with two praetorian prefects subordinate to him .