Answer by taking a quote from the following article:

The Naga people (pronounced [na:ga:]) are an ethnic group conglomerating of several tribes native to the North Eastern part of India and north-western Myanmar (Burma). The tribes have similar cultures and traditions, and form the majority ethnic group in the Indian state of Nagaland, with significant population in Manipur, Arunachal Pradesh and in Assam. The Naga speak various distinct Tibeto-Burman languages, including Anal, Angami, Ao, Chakhesang, Chang, Lotha, Mao (Emela), Maram, Phom, Pochuri, Poumai (Poula), Phom, Rengma, Rongmei (Ruangmei), Sangtam, Sumi, Tangkhul, Thangal and Zeme. In addition, the Naga have developed Nagamese Creole, which they use between various indigenous communities and villages, which each have their own dialect of language.

The Naga hills have been an area of continued resistance as they had long been isolated from outside cultures. The development of a spirit of nationalism and sense of a common identity are relatively new concepts among the Naga people. According to their traditions, each village is an independent republic; initially, they wanted to be free from all outside domination.  Modern education, together with Christian missions, contributed to the politicization of Naga ethnicity. In 1918, a group of educated Nagas formed Naga Club in 1918. The club wrote to the Simon Commission in 1929 demanding that "Nagas should not be included within the Reformed Scheme of India".  On 14 August 1947, the day before India gained independence from British rule, the Nagas were the first ethnic group from the northeast to declare their territory an independent state, not belonging to the new nation. Angami Zapu Phizo led the initial movement with the Naga National Council (NNC). In the last days of the British Raj, he held talks trying to achieve a sovereign Naga nation. In June 1947, a 9-point agreement was signed which promised to bring the Naga tribes under a single political administrative unit and recognised the Nagas' right to self-determination after 10 years. Disputes arose over the interpretation of the agreement, and many in the NNC opposed it.  Under Phizo, the NNC declared their independence from the British on 14 August 1947, a day before India. In May 1951, the NNC claimed that 99 per cent of the tribal people supported a referendum to secede from India, which was summarily rejected by the government in New Delhi. By 1952, the NNC, composed primarily of Nagaland Nagas, led a guerrilla movement. India responded by crushing it with their armed forces. Phizo escaped from the region through East Pakistan and went into exile to London. He continued to inspire the independence movement from there till his death in 1990.

Why do they struggle for identity?