Battle of Yenangyaung
It was now essential to deny the oil fields at Yenangyaung to the Japanese some 100 miles north of Prome.
The allied lines of defence were planned to be from Minhia (west back of the river Irrawaddy) east to Taungdwingyi, and Pyinmana (an important rail junction 50 miles north of Toungoo) to Vith Loikaw. The Chinese Vth Army would defend Pyinmana and Vith Loikaw. But by now 'Vinegar Joe' Stilwell had poisoned relations between himself and the British to such an extent that both sides thought that the other would collapse in front of the Japanese advance. On 1st April Lieutenant-General Slim was visited by Generals Wavell and Alexander at Allanmyo, Corps HQ, 35 miles north of Prome, while, on the same day, the 17th Indian Division around Prome was finally driven out.
On 16 April, almost 7,000 British soldiers, and 500 prisoners and civilians were encircled by an equal number of Japanese soldiers from the Japanese 33rd Division at Yenangyaung and its oil field. The 33rd Division had cut the Magwe road between Slim's two divisions, who were now about 50 miles (80 km) apart. The 1st Burma Division was hampered by large numbers of wounded men and short of water. Major General Bruce Scott, commanding the 1st Burma Division, telephoned General Sun Li Jen, commanding the Chinese 38th Division, asking for rescue soon after the 38th Division entered the area.
General Sun requested to lead his entire division to the rescue of 1st Burma Division, but General Lo Cho-ying, commanding the Chinese Expeditionary Force in Burma, refused. On 17 April, General Sun instead led his 113th Regiment with only 1121 men in the rescue mission. Because the Chinese had no artillery or tanks, Lieutenant General Slim assigned the 7th Armoured Brigade commanded by Brigadier John Henry Anstice to General Sun. The brigade consisted of two regiments (battalions) of M3 Stuart light tanks and a battery of 25-pounder guns.
For the next three days the Chinese and British force attacked southwards. The temperatures reaches as high as 114 degrees Fahrenheit and pall of smoke from the demolished oil wells and refineries hung over the battlefield.
Meanwhile, 1st Burma Division fought its way to and across the Pin Chaung river where they met with the relief column on 19 April. On the next day, the Allied force attacked south toward Yenaungyaung and Pin Chaung where the Japanese suffered heavy casualties, but the Allied forces were too weak to hold the oil fields and had to retreat to the north.