[3] He became aide-de-camp to Major-General Henry Clement Wilkinson, commanding the North-Eastern District at York, in September 1891[4] while he prepared for entrance to Staff College, Camberley.

[1] Birkbeck served throughout the Second Boer War in South Africa as assistant Inspector of Remounts and received the brevet promotion to lieutenant-colonel on 29 November 1900.

He impressed his superiors, the Commander-in-Chief in South Africa, Lord Kitchener, referred to him in a despatch as "perturbed by nothing" and with "considerable ability".

[7] In 1905, he was posted for a year with the Imperial Japanese Army in Manchuria, "where his immense size and genial nature made an excellent impression on our Allies, and led them to help him with much valuable information for his reports.

[9] In September 1912 he reverted to normal pay and served as director of remounts at the War Office, for which he was promoted to the temporary rank of brigadier general while holding this appointment.