The Forty Years' War  was a military conflict fought between the Burmese-speaking Kingdom of Ava and the Mon-speaking Kingdom of Hanthawaddy Pegu. The war was fought during two separate periods: 1385 to 1391, and 1401 to 1424, interrupted by two truces of 1391-1401 and 1403-1408. It was fought primarily in today's Lower Burma and also in Upper Burma, Shan State and Rakhine State. It ended in a stalemate, preserving the independence of Hanthawaddy, and effectively ending Ava's efforts to rebuild the erstwhile Pagan Empire.. How many years separated the two periods of the two truces of the Forty Years' war?