Nyo soon tested his power by meddling into the accession affairs of Hanthawaddy Kingdom, the much larger kingdom to the south. In 1491–1492, Hanthawaddy's new king Binnya Ran II came to power by killing off all the royal offspring. Taking advantage of the chaos in the southern kingdom, Nyo sent a probing raid into the territory of Hanthawaddy without Minkhaung II's permission. At Kaungbya, he killed its Shan governor in single combat by jumping onto his elephant and cutting him down. Hanthawaddy's response was swift. In late 1495, Binnya Ran II sent in a combined land and naval force of 16,000, which ultimately laid siege to the new built Dwayawaddy itself. Toungoo barely survived the siege but Nyo would not make war against the larger neighbor for the remainder of his life.