The Battle of Semarang (), in Indonesia also known as Pertempuran Lima Hari (Five Days' Battle) was a clash between Japanese forces of the Sixteenth Army and Indonesian forces consisting of People's Security Agency personnel and pemuda in October 1945 at the city of Semarang, Central Java. The battle is considered as the first major clash involving the Indonesian military. With the Japanese surrender, Indonesian authorities attempted to seize Japanese arms in anticipation for a Dutch return. Tensions rose after the Semarang garrison refused to hand over their weapons, and after an incident sparked a massacre of Japanese civilians, fighting broke out between the Japanese and Indonesian forces. Background After the August 1945 surrender of Japan in the Pacific War, Allied commander in Southeast Asia Louis Mountbatten following negotiations with a Japanese delegation tasked existing Japanese forces in Southeast Asia to maintain law and order until Allied forces could arrive. By September 1945, many Japanese units in Java had disarmed, surrendering weapons and ammunition to Indonesian nationalists. The city of Semarang in Central Java was also by then largely controlled by Indonesian authorities in form of the Badan Keamanan Rakyat (BKR) and the pemuda. RAF Wing Commander T.S. Tull arrived in Central Java on 18 September as part of a Recovery Allied Prisoners of War and Internee (RAPWI) delegation and concluded that Japanese cooperation was vital to repatriating Allied prisoners. In early October, the 16th Army issued an order for local commanders to let the Indonesian authorities maintain law and order, with the Japanese garrisons to provide assistance. On the other hand, Indonesian authorities and the pemuda wanted to acquire arms in anticipation of a Dutch return to Java. Following negotiations between the Indonesian pemuda, Wongsonegoro (then governor of Central Java), Major General Nakamura Junji (Commander of Japanese forces in Central Java), and Major Kido Shinichirō (Commander of the Semarang garrison), the Japanese garrison at Semarang handed out around 660-700 rifles and 1,600 between 5 to 7 October 1945. Despite having acquired a number of weapons, the Indonesians pressed the Japanese again on the 12th of October for more weapons, but this time the negotiations dragged on, and in the end, Major Kido asserted that the Japanese forces would not transfer further weapons to the Indonesian authorities. This refusal was then followed by Japanese plans to seize Semarang and the Indonesian pemuda's attempts to imprison Dutch and Japanese civilians. Prison