Lieutenant-Colonel George A. Ryan was commissioned into the 70th Regiment as an Ensign in May 1844 and had risen to the rank of Major prior to his arrival in Auckland in June 1861. In the following November took command of a detachment of his Regiment to keep order and protect the town of Dunedin, as disturbances had broken out among the white mining community.

Then in June 1863, two Companies of the 70th, under Ryan's command, moved to Queen's Redoubt on the Waikato River in consequence of a threatened advance by local tribesmen against Auckland. In the subsequent action fought against a large force of Maoris entrenched on the heights of Koheroa on 17 July, the enemy were driven out of their positions by the point of the bayonet, Ryan being favourably 'Mentioned' by General Cameron in his Official Despatch (dated 27.7.1863): 'I cannot speak too highly of all the actions of all the Officers and men engaged, or of the able manner in which the troops were led by their Commanding Officers, [among them was] Major Ryan of the Seventieth'.

Ryan again distinguished himself in the relief of a Militia Post at Pukekohe on 14.9.1863 and at the attack on Gate Pah on 29.4.1864, once again receiving a favourable 'Mention' from General Cameron. Finally, in October 1864, he participated in the successful expedition under Colonel Warre against Te Arei Pah in Taranaki, services that obtained Ryan a Brevet Lieutenant-Colonelcy. He retired in March 1865 with the rank of substantive Lieutenant-Colonel.