He was born into a time of political turmoil caused by the refractory Lords, the Ettuveetil Pillamar as also enemies of Venad such as the Rajah of Kayamkulam.

When Karthika Thirunal was only four years of age, in 1728, his father died foiling an assassination bid by the Kayamkulam Rajah, when the prince along with his parents were travelling from Haripad to the domains of the Vanjipuzha Thampuran, a Brahmin chief, at Budhanur.

Under his uncle's reign, Travancore had gained the reputation of being the most powerful state in Kerala and hence, many of the neighbouring chiefs wished to execute friendship treaties with the Maharajah.

The recollections of the past shady dealings and breach of faith on the part of the Cochin rulers naturally had raised apprehensions in the Maharaja that his neighbour might not adhere to his promise when he felt his position secure.

On the 25th of the Tamil month 'Adi' of 937 ME (1761 AD)[clarification needed] the Raja of Cochin read the terms of their treaty and solemnly swore to abide by its terms, in the presence of the Deity Sthanumoorthy of Suchindrum Temple near Cape Commorin, the ministers of the two kingdoms and the spiritual authorities also being present and the signed document was delivered to the representative of the Maharaja of Travancore.

The Calicut forces suffered heavily in the fight at Trichur and fled precipitately to their fortified stations in Kunnankulam and Chelakara.

In the meantime, the division under D'Lannoy dislodged the Zamorin's men from Cranganore and pursued them beyond the Chetwa river and marching to Trichur by way of Enamakal, found the place already in the occupation of Dalawa Marthanda Pillai.

The combined army then advanced to Chelakara and after a severe engagement, drove the Zamorin's men beyond the northern frontier of Cochin.

In 932 ME, Marthanda Varma had projected the construction of a line of fortifications on the northern frontier, but his death the following year prevented anything substantial being done.

In fact the Dutch records stated that Maharajah Marthanda Varma deliberately refrained from annexing Cochin on an earlier occasion so as to maintain a buffer-state between his kingdom and Mysore of Hyder Ali.

Certain territorial disputes arose between Travancore and the Nawab of Arcot which were eventually settled, though the Maharajah had to part with large sums of money and some territories mainly because the British East India Company's officers had compelled him, as the Nawab was a familiar figure at Madras and his propensities for perpetual borrowing at extra hazardous rates of interest enlisted their sympathies.

The Maharaja obtained in return, lands in Shencottah and the temple at Cape Comorin, which were at the time not part of Travancore but were desired by the Maharajah to round off his dominions.

[5] Hyder Ali had usurped the throne of Mysore and was keen to invade and bring the smaller coastal kingdoms of Malabar and Travancore under his sway.

As early as 1756, he had invaded Malabar at the instance of the ruler of Palghat to help him reg ies captured by the Zamorin of Calicut.

Soon rumours of a proposed invasion of Travancore started developing after the Maharajah refused to stop construction of the Nedumkotta, which passed near the Dutch possessions, through Cochin territories, and because he had given refuge to Hyder Ali's enemies.

While the Rajah of Cochin agreed, Karthika Thirunal of Travancore replied, stating that it was "neither to please him nor in accordance with his advice that the invasion of Malabar was undertaken".

[6] In 1788, a rebellion broke out in the territories and vassal states of Mysore, now ruled by Tipu Sultan, son and successor of Hyder Ali.

Finally in 1789, arguing that the Nedumkotta passed illegally through the territories of Cochin, his vassal state, Tipu Sultan gathered his entire force in Malabar and marched to invade Travancore.

[11] Tipu and his forces reached the Nedumkotta line which protected Travancore's northern frontier and launched an attack in late December 1789.

[12] But a small number Travancore soldiers managed to change the course of events, by opening fire on the 14,000 Mysore infantry from a close cover that killed the Mysorean officer leading a bayonet charge.

His palanquin, seals, rings, sword and other personal ornaments fell into the hands of the Travancore armies under the Dewan Raja Kesavadas Pillai.

[16]In the following weeks, Tipu Sultan, stung by his defeat, complained to the English Governor Holland at Madras in a pre-dated letter that his soldiers were searching for fugitives from Malabar and that it was Travancore which had taken the offensive.

When orders were finally received, it was too late and the British Commander thought it injudicious to commit his soldiers against the large Mysorean army.

A large number of Tipu's soldiers were killed by the sudden flood and the road of succour and assistance to the advance guard was cut off.

Although the Sultan was once again defeated and prevented from gaining any more ground in Travancore, the Dewan increased the garrison of the forts further South and maintained a military force ready for battle in any case.

Meanwhile, Governor-General Cornwallis removed the acting Governor of Madras Mr. Hollond from his post, because he had not provided any aid to Travancore in the battle.

All his kathakali plays attained much popularity and fame on account of its technical superiority in stage presentation, variety and vividness of characters and the story.

He has to his credit seven plays: The maharajah died on 17 February 1798, at the age of 74, after a long reign that was prosperous, save for the invasion of the kingdom by Tipu Sultan.

More importantly, he came to be known as Dharma Raja due to the asylum he provided to the thousands of people from Malabar fleeing to escape forced proselytization by Tipu Sultan.