On 6 July 1898 he was promoted to lieutenant-colonel and became commanding officer of the 3rd Battalion, the Grenadier Guards, and the following year he led the battalion to South Africa following the outbreak of the Second Boer War in October 1899. He was wounded at the Battle of Belmont in November 1899 and mentioned in despatches, but was back with his battalion in time for the Battle of Magersfontein in December. In March 1900 his battalion took part in the march on Bloemfontein and the pacification of the Orange Free State. He escorted Piet Cronjé into captivity, and commented in a letter home: "It is a curious idea taking one’s wife &amp; family with one to the wars &amp; must be inconvenient for many reasons but it is rather the fashion in these parts. Living in a river bed &amp; being shot at every day seems an odd fancy for a lady." On 23 March he was badly wounded when a small foraging party, mainly of officers, which he was leading, including Colonel Codrington of the Coldstream Guards, was ambushed at Karee Siding; his adjutant was killed. This episode was generally regarded as "plucky" but widely reported round the world as an example of the "over-confidence and recklessness" (in the words of the New York Tribune) of British officers. However Crabbe was back with his battalion by the end of April and as they marched north towards Pretoria on 1 May Crabbe was observed and commented on by Arthur Conan Doyle: "Here is another man worth noting. You could not help noting him if you tried. A burly, broad-shouldered man with full, square, black beard over his chest, his arm in a sling, his bearing a medieval knight-errant. It is Crabbe, of the Grenadier Guards."