Q: Generate a correct and concise answer for the question based on the words in the context.
Context : Ian MacAlister Stewart, 13th Laird of Achnacone OBE MC* DSO DL (1895 - 1987) was a Scottish military officer who served in the British Army during both the First and Second World Wars.
Question : In what military organization did Ian MacAlister Stewart serve?
A:
British Army