The 86th Carnatic Infantry was an infantry regiment originally raised in 1794 as the 36th Madras Native Infantry, part of the Presidency of Madras Army which was itself part of the Honourable East India Company Army.
The presidency armies, like the presidencies themselves, belonged to the East India Company until the Government of India Act 1858 (passed in the aftermath of the Indian Rebellion of 1857) transferred all three presidencies to the direct authority of the British Crown.
[1] During World War I they were attached to the 9th (Secunderabad) Division which remained in India, on internal security and training duties.
After World War I the Indian government reformed the army moving from single battalion regiments to multi battalion regiments.
[2] In 1922, the 86th Carnatic Infantry became the 10th (Training) Battalion, 3rd Madras Regiment.