Ayub retired from active service in 1958; however, he was made field marshal in 1959. See "Special report: The Changing of the Guard 1958-1969", Dawn, 2 September 2017:
Dawn October 27, 1959 (News Report)
President Ayub made Field Marshal
General Mohammad Ayub Khan was conferred the rank of Field Marshal by the presidential cabinet. The communique said that the conferment of this rank will serve to demonstrate to the world in a humble way the high esteem in which he is held by his people and how grateful the nation is to its saviour. The rank of Field Marshal is the highest rank of armies built on the patron of the British Army. The press communique added that by a peaceful revolution last year the President had not only defended the territorial integrity of Pakistan but had also saved the very existence of the nation.[2]