Simplify the following text for a Grade 8 native English-speaking person.
Original: He became the Pakistan Army 's first native Commander in Chief in 1951 , and was the youngest full general and self-appointed 5 star rank Field Marshal in Pakistan 's military history .
Simplified: He became Pakistan 's first native Commander in Chief in 1951 . He was the youngest full-rank general and self-appointed field marshal in Pakistan 's military history .