Though the birth of the Nair Militia could be traced to the beginning of the 11th century due to the socio economic conditions of the times, the army on modern lines evolved only during the dawn of the 18th century.

The 9th (Travancore) battalion was raised in 1704 at Padmanabhapuram (now in Kalkulam taluk of Kanyakumari district in Tamil Nadu) as Travancore Nair Infantry to be the personal bodyguards of the Maharajah Ravi Varma (r.1684-1718). It was on the forefront of the Colachel war of 1741 in which the Dutch were completely defeated by Maharaja Anizham Tirunal Marthanda Varma (r.1729-58), the founder of modern Travancore. Captain Eustachius De Lannoy, who was captured as a Prisoner of War in the famous Battle of Colachel was appointed by Marthanda Varma as the Senior Admiral (Valiya Kappithan) and he modernized the Travancore army by introducing firearms and artillery. From 1741 to 1758, De Lannoy was in command of the Travancore Forces and he was involved in annexation of many small principalities like Vadakkumkur, Thekkumkur, Kottarakara Kayamkulam Ambalapuzha, Kottayam,Changanacherry,Meenachil and Karappuram for the Maharajah.

Raja Kesavadas was the Diwan of Travancore (1788-98) under Dharma Raja and he contributed sizably to the modernization the Travancore army by procuring weapons from the Carnatic Nawabs, the Dutch and the English. He increased the number of European officers in the army and ensured the support of the British.

The Mysore invasions towards the end of the 18th century had definite effects on the military organization of Travancore. In 1795, a treaty was entered between the HEIC and the Rajah of Travancore on mercantile affairs and the defence of the country.

In 1817, J.Munro, Resident of Travancore took initiatives to form a disciplined Nair brigade assisted by Captains Mc Leod, Daly and Sheridan. The first and second battalions of the brigade had enlisted 1000 Sepoys each.

A report by Subedar Major Kumaran Thampi of the Nair Brigade dated 27th April 1854 regarding the Militia of Travancore –both ancient and modern- makes interesting reading and can be seen in the book “Socio Economic background of the Military history of Travancore “ by Dr.Krishnan Nadar, which was his PhD thesis .

In 1935, the Travancore State joined the Indian State Forces Scheme and the battalion was named 1st Travancore Nayar Infantry, Travancore State Forces. The unit was reorganized as an Indian State Infantry Battalion by Lieutenant Colonel H S Stewart who was appointed Commandant of the Travancore State Forces. In 1940, the battalion left for Padmanabhapuram and arrived at Military Station, Cannanore. The battalion served overseas in the 1940s. In 1945, Major General Parameshwaran Pillai was appointed GOC, Travancore State Forces. In the same year, the unit was asked to move to South East Asian Command. In Hong Kong, the unit was assigned the task of guarding Japanese prisoners of war, airfields and docks. It also looked after the repatriation of POWs to Japan. The unit left Hong Kong, disembarked at Madras and arrived at Trivandrum on 31 January 1947
The 16th (Travancore) battalion was raised in 1819 as the Travancore Nayar Infantry during the reign of Gowri Parvathi Bayi (r.1815-29)

The 17th (Cochin) battalion traces the origin to the Perumpadappu dynasty from the 15th century and is one of the oldest units. It came to be known as Nayar brigade with strength of 10 officers and 400 men with its function restricted as ceremonial guards at the Palace. It was reorganized as Cochin State force during WW II with one infantry battalion and one garrison company.