Simplify the following text for a Grade 8 native English-speaking person.
Original: The War Office was a department of the British Government , responsible for the administration of the British Army between the 17th century and 1963 , when its functions were transferred to the Ministry of Defense .
Simplified: The War Office was the name of the ministry which controlled the British Army . In 1963 the independent War Office , Admiralty and Air Ministry were joined to create the Ministry of Defense which controls all of the British Armed Forces .