In late 1964, Rumkorem was arrested by military policemen for trying to prevent a government sponsored demonstration in support of the
Act of Free Choice (PEPERA), on the other hand his father in a meeting with Sukarno on 16 October 1962 expressed Act of Free Choice (PEPERA) no longer necessary. He was jailed for three months and then put under house arrest until November 1965. In 1967, he was jailed for demanding that Indonesia take a clear stance on the referendum. He spent most of 1967 in jail before being expelled to Biak. Rumkorem soon became aware of the widespread use of torture, rape and extrajudicial executions of people associated with the
Free Papua Movement (OPM), an organization campaigning for the independence of West Papua. In March 1969, Rumkorem was arrested by the Indonesian Navy for alleging fraud during preparations for the upcoming Act of Free Choice referendum. Rumkorem was imprisoned during the referendum, then placed under house arrest and then sent to
Jayapura. Rumkorem went on to escape from captivity, fleeing to the border with the
Territory of Papua where he founded the OPM affiliated National Liberation Army (TPN) guerilla group. TPN's ideology combined Papuan nationalism and Protestant Christianity. While mostly armed with traditional weapons and understrength, TPN was able to successfully carry hit and run attacks on the Indonesian army while disseminating its propaganda in urban areas. TPN numbered some 19 permanent members, while many OPM activists visited its moving headquarters deep in the jungle to receive military and political training before returning to their villages. In mid 1971, Rumkorem was informed by a coded letter that a group of West Papuan independence activists based in the Netherlands led by
Nicolaas Jouwe planned to form a provisional government in exile. Herman Womsiwor, a political opponent of Jouwe, urged Rumkorem to issue a proclamation of independence before Jouwe's group. On 1 July, Rumkorem's guerillas seized the Waris border post. Brigadier General Seth Rumkorem and Chairman of the Senate
Jacob Prai signed the proclamation of the
Republic of West Papua and transmitted it through the post's shortwave radio. The proclamation established a constitution, senate, army, national flag (
Morning Star flag), state seal and anthem (
Hai Tanahku Papua). OPM agents disseminated news of the proclamation all across West Papua, while army reprisals and government land seizures boosted recruitment. In 1976, a rift emerged between Prai and Rumkorem, a combination of a personality clash between the two leaders and political disagreements. Rumkorem believed that TPN urgently needed weapons and favored requesting assistance from the
Eastern Bloc, while Prai argued that such a move would be contrary to OPM's principles. Rumkorem on the other hand, accused Prai of working with unreliable allies such as Australia. Prai referred to Rumkorem as an "early traitor to the West Papua cause" due to his past affiliation with the Indonesian military. Prai departed the Victoria camp with the majority of its residents to
Ubrub where he founded the Pemka faction and its military wing the Pepenal. Most of Rumkorem's supporters originated from his native Biak and
Tanahmerah Bay. Rumkorem soon offered to serve as Prai's deputy but negotiations broke down when Prai founded a "De Facto Government" with Jouwe. Indonesia seized the opportunity to launch a
large scale offensive against OPM southwest of Jayapura. According to OPM estimates its losses in fighters and civilian supporters amounted to 1,605 killed. Overseas OPM activists claimed that its strength had been reduced to 3,000 to 5,000 fighters, while Indonesian officials believed it had been nearly wiped out. In early May 1977, Rumkorem was ambushed by Pepenal guerillas, but he managed to escape with the core of his group to Papua New Guinea. The Victoria and Pepenal factions continued a three way struggle with the Indonesians until 1984. In May 1982, Rumkorem sailed from
Vanimo to
Vanuatu to obtain weapons, after receiving intelligence about a group of high ranking Vanuatuan politicians sympathetic to his cause. Unbeknownst to Rumkorem the head of his intelligence unit became an Indonesian agent, after being tortured and bribed by the latter. Rumkorem assigned his defense minister Richard Joweni as the temporary head of the movement and departed on a motorized canoe just as Papua New Guinea was about to be struck by a severe storm. Rumkorem's boat broke down in the middle of the ocean and he and his eight companions became stranded on
Rabaul on 14 September. Rumkorem received shelter from a clergyman and fellow West Papuan refugee. ==Exile==