During the First Anglo-Afghan War he was appointed as interpreter and quartermaster to the 33rd Bengal Native Infantry, marching to Peshawar with the army of George Pollock.

[1] In early 1843, he rejoined the 59th Bengal Native Infantry stationed in Ludhiana, indulging in his passion for shikar with hunting expeditions throughout the Punjab.

During the escape of the Sikh cavalry, Lumsden was shot in the foot which left him with a slight but permanent limp for the rest of his life.

A number of these assistants had been brought to Lawrence's attention on the battlefield at Sobraon, including John Nicholson, William Hodson and Herbert Edwardes.

Lumsden later claimed that what first brought him to the attention of Lawrence was an incident a year or two previously, when he and a subaltern had been held prisoner by a gang of robbers following a shooting expedition on the banks of the Sutlej.

[4] Lawrence intended the corps as 'trustworthy men who could at a moment's notice act as guides to troops in the field, collect intelligence beyond as well as within the border.

[1] Lumsden would build up his force into what became the most famous unit of the British Indian Army, inspiring a degree of devotion bordering on idolatry.

They were tasked to unravel a conspiracy believed to have been organised by the Sikhs to sow discontent amongst certain members of the Bengal Native Infantry and Irregular Cavalry stationed in Lahore.

[7] Lumsden with the aid of Muhammad Pir Buksh succeeded in obtaining papers proving the conspiracy and linking it with Maharani Jind Kaur, who he was then charged with escorting from Sheikhupura to Ferozepur.

Following the war, he noted his disappointment that all of Lawrence's assistants, despite their achievements in service, were being overlooked for key political postings at the expense of more junior civilians.

Lumsden initially based his regimental headquarters in a ruin outside of Peshawar, known as the Burj, which had been built in the seventeenth century by a wazir of the Mughal Empire.

[6] Later that year he was part of a force moving against Afridi tribesmen who had attacked engineers building a road through the Kohat Pass killing twelve and wounding eight.

In 1857 he was sent on a mission to Kandahar with his younger brother Peter and Henry Bellew to assess the current military and political situation in Afghanistan.

In May 1857, the Indian Mutiny broke out, causing Lumsden to fear for his safety six hundred miles from the nearest British post in Jacobabad and dependent entirely on the caprice of the Amir.

[12] Lumsden, relying on regular updates from Herbert Edwardes in Peshawar, requested permission to return to India, but his service in Afghanistan was deemed vital in the interests of the Empire by the Governor General.

Therefore, in undertaking the Candahar mission, Major Lumsden missed the opportunity of commanding his corps and of winning rank and distinction before Delhi; while on the other hand he gained little but honour and risk in the interior in Afghanistan".In 1860 he served under his friend Neville Bowles Chamberlain in the Waziri Expedition.

In the spring of 1869, on the invitation of Lord Mayo he travelled to Ambala for the Durbar of Sher Ali Khan, affording him the change to re-acquaint with old friends and comrades.

His friend, Sir Richard Pollock remarked of him in later years: ""A singular mixture of shrewdness and simplicity, absolutely free from selfishness and self-seeking, with great originality, a perfect temper and a keen sense of humour...he disliked civil routine intensely which made him turn down offers of civil employment so affecting his advance".