Kirkham's troops played a major role in the defeat of the 1871 invasion of Tigray by Yohannes's rival for the Ethiopian crown, Emperor Tekle Giyorgis II (Wagshum Gobeze), fighting with conspicuous success in the Battle of Adwa on 11 July.
In recognition of Kirkham's abilities and services, Yohannes promoted his advisor – who had once kept a hotel at Tientsin and had arrived in the country as a ship's steward with the P&O Line – to the rank of general and gave him a substantial estate at Asmara, then in the province of Tigray, and near the Egyptian frontier.
Kirkham's failure to reach the battle site in time to take part in the fighting cost him much of his prestige, some Ethiopian officers describing him as "an old woman" for his dilatoriness.
The sailors wished to free him, but upon enquiry via cable to London, the naval party was informed that Kirkham had sacrificed the right to British protection by taking service with Yohannes.
Bourke described him as "a fair, rather good-looking, slim man" who was shabbily dressed in "an undress general's uniform with a large sword clanking by his side" and thin old button boots "which were rather trying to his poor feet on the rocks."