Hinomaru, reflecting the red and white of the Indonesian flag. The People's Security Bureau was then, in October, re-organized to form the nascent formal armed forces. This marked the birth of the Indonesian Air Force on 9 April 1946. However, tensions rose as the Dutch tried to re-claim their former colony and launched an assault on 21 July 1947, destroying most of the planes on the ground. Some planes survived though and were hidden in remote bases. 29 July 1947 was date of the first air operation by the newborn air force as three surviving aircraft, comprising two Yokosuka K5Y1 Willow (Cureng) and a Mitsubishi Ki-51 Sonia (the fourth aircraft, a Nakajima Ki-43 Oscar (Hayabusa) flown by Air Cadet Bambang Saptoadji, should also have been involved in the raid as an escort, but as of when it was launched, the aircraft was not airworthy due to engine troubles) conducted air raids at dawn on the Dutch Army barracks in Semarang, Salatiga and Ambarawa, dropping incendiary bombs. Tactically, these raids did not have any effect on the Dutch positions, but psychologically, it was a great success as it proved that the Indonesian Air Force still existed. The Dutch had previously claimed the destruction of Indonesian Air Force in their assault before and they never expected any attack from the sky. Dutch Curtiss P-40E Warhawks tried to find all the guerrillas' planes, but they were too late to find those "ghost" aircraft which landed quickly in Maguwo Air Base, near Yogyakarta (now, Adisucipto International Airport). Indonesian pro-independence guerrillas tried to save captured aircraft in a number of remote areas, including examples of the Mitsubishi A6M Zero-Sen "Zeke", Aichi D3A "Val", and Mitsubishi G4M "Betty". Under pressure from the United Nations, the Dutch finally agreed to acknowledge Indonesian independence. Following the 1949 Round Table Conference, sovereignty was officially transferred to the United States of Indonesia. The Dutch armed forces left (but remained in West Papua until 1963) and the aeroplanes were handed over to the Indonesians. These comprised, among others, North American P-51 Mustang, North American B-25 Mitchell, North American T-6 Texan, Douglas A-26 Invader, Douglas C-47 Dakota and Consolidated PBY-5A Catalina, which served as the main forces of the Indonesian Air Force for the following decade. During this era, Indonesia received its first jet aircraft; De Havilland DH-115 Vampire. It was also during this era that the national roundels were changed to