Japanese conquest of Burma main attack westward from Rahaeng in Thailand across the Kawkareik Pass. The 16th Indian Infantry Brigade of the 17th Indian Division guarding this approach retreated hastily westward. The Japanese division advanced to Moulmein at the mouth of the Salween River which was garrisoned by the 2nd Burma Infantry Brigade. The position was almost impossible to defend, and had the River Salween, almost wide, behind it. The 2nd Burma Brigade was squeezed into a progressively tighter perimeter, and eventually retreated over the river by ferry on 31 January after abandoning a large amount of supplies and equipment. Part of the force
Mae Hong Son Province Moei, ). Most of the areas of Mae Hong Son Province are the complex mountain ranges of the Thai highlands, parts of which are still covered with rain forest. Of the approximately 6,976,650 rai of national forest reserves, it is estimated that 88 percent is pristine virgin forest. The Daen Lao Range, in the northernmost portion of the province, marks the northern boundary between Thailand and Burma, while the Dawna Range in the west serves as the boundary between Thailand and Burma. The Thanon Thongchai Range in the east of the province serves as the boundary between the provinces of