[3] In 1862 he went with his regiment to India under General Henry Tombs VC, and rose to the level of Executive Engineer as part of a series of public works in the Bengal area.

Dundas was 22 years old, and a lieutenant in the Bengal Engineers, Indian Army during the Bhutan War when the following deed took place on 30 April 1865 at Dewan-Giri, Bhutan for which he was awarded the VC in a joint citation with Major William Spottiswoode Trevor: For their gallant conduct at the attack on the Block-house at Dewan-Giri, in Bhootan, on the 30th of April, 1865.

Major-General Tombs, C.B., V.C., the Officer in command at the time, reports that a party of the enemy, from 180 to 200 in number, had barricaded themselves in the Block-house in question, which they continued to defend after the rest of the position had been carried, and the main body was in retreat.

Major-General Tombs states that on speaking to the Sikh soldiers around him, and telling them in Hindoostani to swarm up the wall, none of them responded to the call, until these two Officers had shewn them the way, when they followed with the greatest alacrity.

[6] In March 1877, he had inherited the family estate of Ochtertyre, near Stirling in Scotland, from his uncle Sir David Dundas MP.

"The Dundas Bridge", between Kabul and Bagram, Afghanistan, was named after him, by the British Army, Royal Engineers, following reconstruction work during 2002.