Hakkenberg was the sole survivor of the 10 brothers and cousins that volunteered for service at the break of WWII. Motivated by a more than average sense of purpose, justice and a sincere love for the land Hakkenberg fearlesly engaged in an almost personal battle with the gangs and guerrillas in the area where he was responsible to restore peace and order during the chaos of the Indonesian revolution. For the same reasons he saw to it that the Dutch soldiers treated the people well.
Responsible for countless legendary arrests he often made alone at night time, he was knighted and awarded the highest military honours. Hakkenberg would regularly hike alone into Republican territory to negotiate with the kampung (village) heads, inquire with his numerous informants and also speak with or even tell off his adversaries. Confident but never foolhardy he seemed endowed with a supernatural sense of timing.
In 1941 at the age of 17 he volunteered to join the Dutch Royal Navy to fight Nazi Germany in the European arena. After their training volunteers were needed home in the Dutch East Indies due to the increasing threat of the Japanese Empire. Aboard the admiral class destroyer HNLMS Kortenaer he was the youngest sailor on February 27, 1942 to engage the Japanese navy in the Battle of the Java Sea. His vessel was torpedoed and sunk. Hakkenberg was rescued by the HMS Encounter and brought to Surabaya.
On March 8, 1942 the Dutch East Indies capitulated to the Japanese and Hakkenberg became an allied POW. As POW he was a captive in Thailand, a forced labourer on the Burma Railway and finally in 1944 a forced labourer in the Japanese coal mines.
After the Japanese capitulation Hakkenberg was the only one of his 10 brothers and cousins who survived the war. He remained at arms in the Navy and became a Marine serving throughout the Indonesian national revolution. After the independence of Indonesia he continued his military career until retiring in 1974 as a Sea Lieutenant of the Marine Corps.
Hakkenberg was the energetic mission leader or solo combatant involved in many crucial tactical actions mostly carried out at night and alone or with a small detachment. For five prominent actions, carried out between 24 August 1948 and March 6, 1949, he was assigned the Military William Order fourth class.
The Royal Decree no.40 of 6 March 1951 stated:
...distinguished in battle by great acts of courage, and loyalty as commander of a detachment of the Marine brigade from September 1947 to May 1949 in the fight against terrorist gangs (and TNI units) in East Java, where he was head of only a very small group - sometimes not more than three to five men. He actions were successful [...] without suffering losses, due to namely: his excellent knowledge of the language, country, people, (traditions) [...] his fearlessness in particular.
- a. On August 24, 1948 in Daragowak the influential gang leader Tai Pa with five of his henchmen were arrest alive;
- b. On 25 October 1948 in Jakarta he infiltrated a TNI group to surprise and imprison them;
- c. On 7 and 19 April 1949 on the south of Mentoeroe he inflicted losses on a powerful adversary;
- d. On February 14, 1949 he overpowered and arrested the Chief of Staff of the TNI confiscating very valuable information;
- e. On March 6, 1949 he arrested the Republican resident of Madiun with some other prisoners, despite fierce opposition.
"optreden van een individualist'' Biography on '' Militaire Willems-Orde'' website of the Delft Army Musuem.