Simplify the following text for a Grade 11 native English-speaking person.
Original: He is noted for his military tactics and prowess , commanding the forces of Medina and those of his immediate successors of the Rashidun Caliphate ; Abu Bakr and Umar .
Simplified: He is famous for his military success , as he commanded the forces of Muhammad and of his immediate successors Abu Bakr and Umar ibn al-Khattab .