After buying the rank of Ensign in the 99th Regiment of Foot in 1852, Pearson served during the Crimean War where he was Mentioned in Despatches.

After steadily rising through the ranks, Pearson was sent to South Africa to command a battalion of the 3rd Regiment of Foot (the Buffs).

Pearson was placed in command of a column of infantry which then became besieged at Eshowe for 70 days until Lord Chelmsford relieved them.

[6] After a period on half pay, he returned to active duty on 7 August 1857, transferring to 3rd Regiment of Foot (the Buffs),[7] and purchased his promotion to major on 2 May 1865.

1 Column had repelled a Zulu advance, this engagement apparently included the first use of a Gatling gun by British forces.

[13] For his actions throughout South Africa he was Mentioned in Despatches a further 10 times,[1] and appointed a Companion of the Order of the Bath (CB) whilst he was still fighting,[14] On 6 October 1879 he received a hero's welcome in his home town of Yeovil, the church bells were rung, he was greeted by the Mayor, who compared him with previous West Country heroes such as Drake, Grenville, Raleigh and Hawkins, and presented with a specially inscribed sword.

[2] The war was already somewhat controversial, the actions by Sir Bartle Frere and Lord Chelmsford which began it had not been specifically authorised by the British Government in advance, and the disaster at Isandlwana led to the defence of Eshowe by Pearson, and the famous action at Rorke's Drift being used to distract from the failure there.

[15][16] At this reception, Pearson defended the conduct of the war, and was supported by Sir Percy Douglas, who had preceded Chelmsford as the commander of British forces in South Africa.

[1][24] On 22 December 1899, he travelled to Southampton as part of the send off for his old battalion, 2nd Buffs, who were departing for South Africa once again, this time to fight in the Boer War.