Manipur and Assam became involved in the disputes between Thailand and Burma, and Manipur took advantage of a Burmese invasion of Thailand to raid deep into its western frontier. This triggered the Burmese invasion of Manipur and Assam, which sucked in the British, ruling neighbouring Bengal. The British, to safeguard their position against the Burmese, intervened, defeated Burma and took over Assam, and brought Manipur under British paramountcy in 1891.
During the Second World War, Manipur was the scene of many fierce battles between the Japanese and Allied forces. The Japanese swept over East Asia and came up to Manipur. They were beaten back before they could enter Imphal and this proved to be one of the turning points of the War.
There are two cemeteries maintained by the British War Graves Commission in Manipur, which are the final resting places of several Indian and allied soldiers who died here.
In 1947, with British Parliament's repeal of British Paramountcy, in preparation for Indian independence, Manipur became an independent kingdom once again.
The King, Maharaja Budhachandra, began a process of democratisation of the state, enacting the Manipur Constitution Act, 1947, which established a democratic form of government with the Maharaja as the Executive Head and an elected legislature.
In 1949, the King Budhachandra was invited to Shillong, capital of the Indian province of Assam, where he signed an agreement for merging the kingdom into India. Some feel that this signing was under pressure, although no force was used. The King had already signed the Instrument of Accession with the Indian Dominion in 1947.
Once Manipur became part of the Indian Union, India dissolved the State's Constitution Assembly in October, 1949, and made it into a part C state. Lateron it was further degraded to the status of the union territory from 1956 onwards.
In 1972, Manipur was elevated to the status of a state (or province).