Robertson was finally breveted as a lieutenant colonel in June 1936. The rank became substantive in July 1937. Like other regular officers, Robertson was opposed to the "Singapore strategy", and therefore to the defence policy of the government of the day, and said so publicly in the British "Army Quarterly". Robertson argued for a local defence of Australia by land and air units. The naval theorist, Admiral Sir Herbert Richmond, responding to Robertson's arguments in an editorial, pointed out that local defence would fragment the British Empire's defence effort and could not secure the sea lanes. However, in view of the weakness of the Royal Navy, Richmond was forced to concede that Robertson's approach was not unreasonable.