After defecting to the Indonesian guerrillas who opposed Dutch rule, he lived the rest of his life in Indonesia, where he became a human rights activist and political dissident.

[citation needed] In 1942, at age 17, he was accepted as an economic counselor at Teppemaand Vargroup Groothandel voor Chemische Producten, a chemical company in The Hague.

[citation needed] Reluctant to take part in the war, Princen fled to France – but upon hearing that his mother was ill, came back and was arrested by the Marechaussee and detained at Schoonhoven.

[citation needed] Also aboard the Sloterdijk was the Communist Piet van Staveren, likewise a reluctant conscript who would eventually desert and join the Indonesian rebels.

[citation needed] During the assault upon the provisional capital, the nationalist rebels released Princen from their prison and gave him the chance to enlist in the Tentara Nasional Indonesia (TNI, Indonesian Republican Forces).

[citation needed] When he joined them, the pro-independence forces' fortunes seemed at their nadir, with their political leadership captured and most of the territory of Indonesia under a re-established Dutch military rule.

[citation needed] Princen was fully committed to his new cause, seeing front-line service under Kemal Idris and taking part in the fighting retreat of the Siliwangi Division under then-Colonel A. H. Nasution, from Central Java to "guerrilla cantons" established in West Java – an action which came to be known as the Long March Siliwangi (derived from the famed Long March of Mao Zedong's Chinese Communist Party).

In a struggle decided as much in the international public opinion and diplomatic forums as in the field, the presence of an articulate ex-Dutch soldier with an anti-Nazi past in the rebel ranks had a political and propaganda significance.

Some accused him of having allowed himself to be used as bait to draw Dutch soldiers into an ambush which led to a high number of KNIL (Koninklijk Nederlands Indisch Leger - Royal Netherlands East Indies Army) fatalities.

[citation needed] The decoration he received from Sukarno – a small five-pointed bronze star on which were etched the words "Pahlawan Gerilja" (Guerrilla Hero), and which Princen conspicuously displayed until the end of his days – was to give him at least some protection from the most harsh forms of repression to which successive Indonesian regimes resorted against many other dissidents and political opponents.

[citation needed] After the war Princen married again – this time to a Dutch woman named Janneke Marckmann (until 1971) and later to Sri Mulyati, who was to remain his companion until his death.

He was apparently one of the "obstructing parliamentarians" whom Sukarno found annoying and whose activity was among the factors which led the President to replace the Western-type parliamentary system with "guided democracy" in 1959.

[citation needed] In 1966 Princen founded and headed Lembaga Pembela Hak-Hak Azasi Manusia (Indonesian Institute for the Defense of Human Rights).

It was the first human rights organization in Indonesia, and which handled many high-profile cases during the years of the Suharto dictatorship and provide a reliable alternate source of news to Western journalists in Jakarta.

[citation needed] Among the earlier campaigns which Princen conducted was on behalf of the left-wing writer Pramoedya Ananta Toer, imprisoned and tortured by the Suharto regime.

[citation needed] This was followed in the early 1970s by Princen's prominent role in creating a larger organization, the Indonesian Legal Aid Institute (LBHI), where he met with many other human rights figures including Adnan Buyung Nasution, Frans Winarta, Besar Mertokusumo, Yap Thiam Hien, Victor D. Sibarani, Mochtar Lubis, Albert Hasibuan and members of the younger generation of activists.

Visitors to his succession of small offices in the early '90s remember calling on him to find themselves welcomed by Princen resting in his underwear, and his close friends recall that it was seldom that they were able to leave before parting with a contribution to help pay his driver or his phone bill.

[15] In the early 1990s, he was a founding member of the Petition of Fifty, a movement for democratic reform which included conservative military figures who had fallen out with Suharto and which for the first time in decades raised a real challenge to his rule.

Along with other members of the group including Ali Sadikin and Hoegeng, Princen again found himself persona non-grata with the regime, although he joked to his visitors that by that time he was "too old to put in jail again".

[16] In 1994 Princen flew to Geneva to testify before the United Nations Commission on Human Rights about the use of torture by Indonesian forces in East Timor and Aceh.

The death sentence passed on him in absentia was no longer in force, but he was considered to be banned from entering the Netherlands, having forfeited his Dutch citizenship and the right to visit.

[18] Dutch left-wing activists defended Princen strongly, and asserted that his continuing rejection was an indication of the country's refusing to come to terms with its dark colonial heritage.

"Poncke Princen was no hero, martyr or saint, but first and foremost a human rights activist," the minister told Radio Netherlands[20] In February 2009 the documentary The White Guerrilla made by the Dutch research-journalist Bart Nijpels appeared on Dutch television (Katholieke Radio Omroep), reconstructing his life and giving an impartial opinion about his political choices.

[citation needed] In March 1998, the 73-year-old Princen – on a wheelchair and undergoing what was described as "mutilating surgery" for his skin cancer – was among some 150 activists who openly violated a ban on political protests in the capital Jakarta, demonstrating against the undemocratic re-election of Suharto and defying the police to arrest them.

There were noted activists and human rights lawyers such as Luhut Pangaribuan, Muchtar Pakpahan, Hariman Siregar, Jopy Lasut and Gurmilang Kartasasmita.

[citation needed] His American friend Max White remarked: "When I learned who was at the memorial service, and at the mosque and cemetery, I was struck by how wide a swath of Indonesia mourned him: from former 'tapols' [political prisoners] to members of the government and military".

[citation needed] He was also mourned in the East Timorese capital Dili, where Xanana Gusmão – soon to be inaugurated president – said that he was deeply saddened by Princen's death: "He was my friend, and he encouraged us in our struggle.