Short answers, pulled from the story.
The Burma campaign ran from January 1942 to August 1945, making it the only continuous land campaign fought by the Western Allies in the Pacific Theatre from the start of hostilities to the end of the war. The monsoon rains limited effective fighting to just over half of each year, which was one of several factors that extended the campaign over more than three years.
The Allied side was drawn primarily from British India, with British Army forces equivalent to eight regular infantry divisions and six tank regiments, 100,000 East and West African colonial troops, Chinese forces including the American-trained X Force and the Yunnan-based Y Force, and smaller contributions from other Dominions and Colonies. Japan was supported by the Thai Phayap Army, the State of Burma's Burma National Army under General Aung San, and the Indian National Army under Subhas Chandra Bose. By 1944, British Empire forces alone peaked at around 1 million land and air personnel.
Imphal and Kohima were the sites of Japan's 1944 invasion of India, Operation U-Go, launched on the 8th of March by the Japanese Fifteenth Army. The siege of Kohima lasted from the 5th to the 18th of April; the siege of Imphal was lifted on the 22nd of June when IV Corps and XXXIII Corps met at Milestone 109. The Japanese suffered between 50,000 and 60,000 dead and 100,000 or more total casualties, making it the greatest defeat in Japanese history to that date, and the battles have since taken on huge symbolic value as the turning point of the war in the East.
The Indian National Army was a force formed largely from Indian soldiers captured in Malaya and Singapore, along with Tamils living in Malaya, and was led by Subhas Chandra Bose under the Provisional Government of Free India. It fought alongside Imperial Japan, particularly during Operation U-Go in 1944. After the failure of that offensive, the INA was shattered, with entire units deserting or surrendering, and its remaining soldiers were reduced to auxiliary duties for the rest of the war.
Rangoon was recaptured on the 2nd of May 1945 as part of Operation Dracula, an amphibious assault by units of XV Corps. A Gurkha parachute battalion was dropped on Elephant Point on the 1st of May to clear Japanese rearguards. When the 26th Indian Infantry Division landed the next day, they found that General Kimura had already ordered the city evacuated on the 22nd of April. The monsoon rains began in full force on the afternoon of the 2nd of May, hours after the Allied forces secured the city.
The campaign had a direct impact on post-war independence movements. The pre-war push among the Burmese population for independence combined with the economic ruin caused by four years of fighting made it impossible to restore the former colonial regime. Within three years of the war's end, both Burma and India were independent. American historian Raymond Callahan noted that General Slim's victory helped the British leave Asia with some dignity, in contrast to other colonial powers.