[3] When the Second Boer War broke out in late 1899, Ritchie was temporarily appointed Adjutant of the newly established 4th (Militia) Battalion of the West Yorkshire Regiment, which was sent to South Africa.

[5] On the outbreak of the First World War, Ritchie was a Lieutenant-Colonel commanding the 1st Battalion Seaforth Highlanders, based in India.

The battalion was mobilised as part of the 7th (Meerut) Division in Indian Expeditionary Force A, and sent to France, where it arrived in October 1914,[6] and first saw action on 7 November.

[10] He was wounded in May 1917, and, after recovering from his injuries, and after being promoted back to temporary major general in May 1918,[11] returned to command the 16th (Irish) Division.

[4] Following the end of the war, Ritchie was confirmed in the rank of major general in June 1919,[12] and briefly commanded a division from August 1919 until January 1920.