His father Lucas Rumkorem [id] was among the founders of the Indonesian Independence Party (PIM) in September 1945 and Tentara Tjendrawasih Tjadangan (TTT) in 1958,[2] whose aim was to incorporate Netherlands New Guinea into Indonesia.

While TTT smuggled important positions and locations in Papua to Indonesian Embassy in Singapore, Ambon, Serui, and Hollandia through the use of Papuan Tionghoa intermediaries and training for Operation Trikora.

[4] Seth likewise enthusiastically welcomed the Indonesians, after working for nine years as a bookkeeper for KLM Royal Dutch Airlines he applied to the Infantry Education Center in Bandung, West Java.

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.

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.

[8] 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.

[9] 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.

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.

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 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.

[6][16] Rumkorem eventually realized that he was betrayed and after receiving intelligence that the Indonesians were carefully monitoring all border crossings to capture him, he opted to continue his political struggle from abroad.