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In 1936 the post of Minister for Co-ordination of Defence was established , though he did not have a department and the heads of the three services - the First Lord of the Admiralty for the Royal Navy , the Secretary of State for War for the Army and the Secretary of State for Air for the Royal Air Force - continued to attend Cabinet .
 Defence, Admiralty, Royal Navy, Army, Royal Air Force
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Defence, Admiralty, Royal Navy, Army, Royal Air Force