The Nedumkotta was a defence fortification constructed along the northern borders of the erstwhile Travancore allied Cochin State of 1757–1762 AD. The places north of Nedumkotta was under Zamorin occupied Cochin (1757–1762). It passed through the territories of the then Cochin State. The Nedumkotta was built primarily to resist the invasion under
Hyder Ali Khan against Travancore State and southern parts of Cochin State. It was raised mainly with clay and mud, and reinforced with stones, laterite and granite at strategic places. It started from the
Krishan Kotta on the west coast, above
Kodungallur, and stretched up to the
Anamala Hills on the
Western Ghats. It was about 48 km long, 20 feet wide and 12 feet high. The lines consisted of a ditch, sixteen feet wide and twenty feet deep with a thick bamboo hedge, a slight parapet and rampart and bastions on rising grounds almost flanking each other from one side of the lines to the other. Its alignment was along the
Periyar river on the west coast up to
Chalakudy from where it went along the
Chalakudy river up to the
Annamalai Hills in the east. There were underground cells to store gunpowder and other war materials, special chambers for soldiers to live, and look-outs and mounted field-guns all along the fortification. On the north side of the fortification, ditches were dug twenty feet wide and sixteen feet deep, and filled with thorny plants, poisonous snakes, and hidden weapons. On the south side as well as on the top of the fortification, wide roads were laid for the convenience of military movements. The construction work was started in 1762 and was completed only by 1775 from where it was extended to
Vypin. Much to the dislike of Tippu Sultan, parts of the Travancore Lines were built on Cochin territory and a large part of the Cochin State was behind Travancore lines. This was a violation of Mysore's territorial agreement and was considered as an encroachment of its territory. Tippu Sultan contacted Travancore Raja to destroy the Lines as early as possible. Tippu Sultan wrote to the Raja, "The Cochin Raja has been my tributary fifty or sixty years – after I possessed the Calicut country you erected lines on a part of the Cochin country. This conduct is not proper, you must demolish the line", to which Cochin Raja replied that the areas where the Lines were established was given to him earlier than the Cochin country became a tributary to Mysore, quote, "I possessed it and had lines were erected on it when I was included in the Treaty of peace which the Honourable English Company made with you. If I had not a right to it, why did you then not demand it". In about June–August 1787 after learning about the geography of Malabar and Travancore and constructing several roads leading into Travancore both from the north by coastal side and from the east by the
Cambam and
Guddalur passes, Tippu Sultan then invaded Malabar. He persecuted the people and chiefs, massacring all those who refused to take up Islam. Many families including that of
Samoothiri fled Malabar and took refuge in Travancore. Around 30,000 noble Brahmin families were sheltered under the Dharmaraja of Travancore. This angered Tippu and he wanted Cochin to surrender all those families who fled Malabar, but the Raja refused to give in. Tippu could not make a bold appeal to the war as Travancore was included in the Peace Treaty between Mysore and the East India company as a friendly country to the company. Tippu then resorted to
Samoothiri to attack Cochin, promising him in return the restoration of a portion of his territory, to which Samoothiri promptly refused. Tippu then requested the help of the Cochin Raja to speak to Dharma raja to become a tributary of Mysore which was then was defied by stating that nothing would be done against the will of the East India Company. This enraged Tippu, who planned then to invade the Travancore demolishing Nedumkotta. The Maharaja informed the Madras Governor, Sir
Archibald Campbell, the proceedings and requested him to lend him 4 English officers and 12 Sergeants to command his army and, anticipating an early invasion by Tippu, commanded
Dewan Kesava Pillai to look to the frontier fortifications. The governor then wrote to Tippu that an invasion against Travancore would be considered as a breach of the Treaty made with the Company. He also offered two or three battalions to assist Raja in his frontiers. Two regiments under Captain Knox were stationed near
Ayacotta for the first time and Mr. George Powney, a Civil Officer, was sent as an agent of the Company to the Travancore Court. Travancore Raja also entered in to a treaty with Dutch Army by which he was handed over the
Cranganore Fort and
Aycotta. ==The structure==