The only region in which Singu maintained military action was Manipur, where he inherited another war from his father. The former Manipuri king Jai Singh, whom the Burmese last drove out in 1770, made four more attempts to oust the Burmese nominee between 1775 and 1782 from his base in Cachar. The Burmese drove him back each time but were unable to capture him. The army gained "barren victories" in Cachar and Jaintia where the rajas of the two small states agreed to pay a token tribute. But the tribute came at a high cost: the army lost 20,000 men, partly by fever over the years. After Singu's dethronement in 1782, the new king, Bodawpaya stopped the invasions. Manipur was again independent.
Question: How many years has the Burmese four attempts to oust the nominee from his base in Cachar lasted?
Answer: 4