Beasley was born in 1876 in Jhansi in Uttar Pradesh, India, where his father was a minister. He was educated at Bedford School, and entered the Royal Military Academy (Woolwich) on leaving school. Beasley was gazetted to the Royal Artillery in 1896. He served in India, Burma and China, and took part in the Relief of Peking after the Boxer Rebellion. He served in the First World War on the staff of the Anzac Corps. He was thrice mentioned in despatches and awarded the Distinguished Service Order (DSO). After the war he served in Germany on the Disarmament Commission. He was an interpreter in French, German and Hindustani.