The 'Battle of Oktwin' was fought between Japanese and Chinese forces as the second battle of the 'Battle of Yunnan-Burma Road' within the Burma campaign (20/23 March 1942).
On 20 March, as Lieutenant General Shojiro Iida’s Japanese 15th Army moved to the north through Burma, its 143rd Regiment and elements of the 55th Cavalry Regiment, detached for the separate task of capturing Tavoy and Mergui, of Lieutenant General Hiroshi Takeuchi’s 55th Division attacked the positions of the Chinese 5th Army Cavalry Regiment to the north of the Kan river, driving the Chinese forces back with heavy losses. Most of the Chinese were then withdrawn to an area to the north of Toungoo, leaving only single companies of cavalry and infantry to delay the advancing Japanese. Meanwhile, Major General Dai An-lan, commander of the Chinese 200th Division, moved his formations into the fortifications which had been constructed at Oktwin and around Toungoo. These defences had been built of timber, which was in abundant supply, and all the positions had been carefully concealed. On 21 March, Japanese forces brushed aside the delaying forces and reached the 200th Division’s outposts at Oktwin.
The 55th Division's 112nd Regiment attacked the 200th Division’s positions at first light on 22 March but made little headway. The Japanese forces attacking the positions occupied by the 1/600th Regiment were one infantry battalion and several pieces of artillery. The Japanese then despatched a cavalry forces round the Chinese left flank, and the position was stabilised only after reservee forces of the 1/598th Regiment had been committed in counterattacks.
The Japanese were now more careful after their vanguard had been ambushed, and used their artillery and machine guns to fire at suspected positions before committing their infantry. Light machine guns were positioned up among the trees and caused many Chinese casualties. Eventually the Chinese set up their heavy machine guns to deal with this menace.
On 23 March, the Japanese attacked once again on the left flank with strong artillery and air support. The battle continued until 16.00 without much success for the attackers, who then tried another flanking move with a company of infantry and scores of cavalry troopers around the right-hand side of the Chinese positions. The Chinese held their ground until the fall of night and only then fell back to their main defensive line at Toungoo on 24 March.