On 20 November 1945, Allied troops under the command of Brigadier Bethell landed in Semarang to disarm Japanese troops and liberatePOWs still detained in concentration camps in Central Java. Initially, the troops were welcomed in the area, with Central Java's governor Wongsonegoro agreeing to provide them with food and other necessities in return for the Allies' promise to respect Indonesia's sovereignty and independence. The Netherlands Indies Civil Administration were also in Semarang, and welcomed the British presence. However, when Allied and NICA troops began freeing and arming Dutch POWs in Ambarawa and Magelang, many locals were angered. Relations were further ruined when the Allies began disarming members of the Indonesian Army. Indonesian troops under the command of Lieutenant Colonel M. Sarbini began besieging Allied troops stationed in Magelang in reprisal for their attempted disarmament. Indonesian presidentSukarno intervened in the situation to calm tensions, and the Allies secretly left Magelang to their stronghold in Ambarawa. Sarbini's regiment followed the Allies in pursuit, and was later joined by other Indonesian troops from Ambarawa, Suruh, and Surakarta. Allied troops were later driven out of the nearby village of Jambu by the combined force of the Indonesian Army. At the village of Ngipik, Allied troops were once again forced to retreat by the Indonesian Army, after attempting to establish control over two villages around Ambarawa. Indonesian troops under the command of Lieutenant Colonel Isdiman tried to free the two villages, but Isdiman was killed in action before reinforcements arrived. Commander of Division V Banyumas, Colonel Soedirman, vowed to avenge Isdiman's death and called in reinforcements to besiege Allied positions in Central Java. On the morning of23 November 1945, Indonesian troops began firing on Allied troops stationed in Ambarawa. A counterattack by the Allies forced the Indonesian Army to retreat to the village of Bedono.
Battle
On 11 December 1945, Soedirman held a meeting with various commanders of the Indonesian Army. The next day at 4:30 AM, the Indonesian Army launched an assault on the Allies in Ambarawa. Indonesian artillery pounded Allied positions, which were later overrun by infantry. When the Semarang-Ambarawa highway was captured by Indonesian troops, Soedirman immediately ordered his forces to cut off the supply routes of the remaining Allied troops by using a pincer maneuver. The battle ended four days later on 15 December 1945, when Indonesia succeeded in regaining control over Ambarawa and the Allies retreated to Semarang.
Aftermath
The Palagan Ambarawa Monument in Ambarawa was erected in memory of the battle. The battle's anniversary is also celebrated as Indonesian Army Day by the personnel and veterans of the Indonesian Army.
