Fort Willem I, Ambarawa

Fort Willem I, known in Indonesian/Javanese as Benteng Pendem Ambarawa ("Ambarawa sunken fort"), is a 19th century Dutch fort in Ambarawa, Central Java, Indonesia.

History
In period of Diponegoro War (1827-1830), Colonel Hoorn, Military Commander in the 2nd division to the crossroads at Bawen (point of junction of the roads connecting Semarang-Yogyakarta and Semarang-Salatiga) instructed the construction of logistic storage, as well several military barracks, to gave immediate supply and forces for the war. Simple bamboo sheds was established at this strategic point.

After the War, during the reign of Willem II, the place of the bamboo sheds proved very strategic. So a new modern fort was constructed at the former bamboo sheds area between 1834-1853. In 1840, Ambarawa grew as one of a strategic military outposts along the route between Semarang and Surakarta. The VOC had established several military defense points along this route which connects Semarang - Ungaran - Salatiga and Surakarta. The purpose of the establishments of these defense points was to establish relationship with the Sultanate of Mataram.

From 1853 to 1927 KNIL military barracks were set up in the fort. The private Dutch East Indies Railway Company (NIS) received concession in 1862 to built a rail track connecting Semarang, Surakarta, Magelang and Yogyakarta with a branch toward Fort Willem I. Construction started in 1863 and was completed in 1873. An earthquake occurring on July 16, 1865 damaged some buildings inside the fort. In 1927, Fort Willem I was adjusted from penitentiary of children prisoner into a penitentiary for political prisoner and adult prisoner.

During the period of Japanese occupation, Fort Willem I was converted into an internment camp.

After the Indonesian declaration of independence, from October 14, 1945 to November 23, 1845, Fort Willem I was used as the headquarter of the Tentara Keamanan Rakjat ("People's Security Army"), a predecessor of the Indonesian National Army. From this year, the prison was used as military barracks with some parts converted into prison. During the Great Awakening period between October 14 to December 10, 1945, around 3,500 Dutch civilians were interned by Indonesian freedom fighters inside the Fort Willem I; the internment camp used former prisoners and guards for camp security.

In 1950, parts of the fort were converted into adult penitentiary. In 1985, it was repurposed for juvenile penitentiary facility; in 1991, penitentiary class IIB; in 2003 until now, penitentiary class IIA.

The fort
Fort Willem I is situated in the middle of a rice field. The main building is a square-shaped fort of 178 x 178 meter. Small storage buildings were situated around 94 meter away from the fort at each cardinal points.

Unlike earlier 18th-century fort designs, the 19th-century Willem I Fort were designed for a defense work of military logistic. Concerning this function, Fort Willem I contains no embrasure nor bastions. Instead there are many windows in the rampart, and the bastions are detached from the fort.