[4][5] They were former Balao class submarines that were loaned to the Netherlands by the United States under the Mutual Defense Assistance Program (MDAP).

[10][11] In the early 1950s this led to the US loaning two submarines to the Netherlands under the Mutual Defense Assistance Program (MDAP), which together would later form the Walrus class.

[13] Before both submarines were transferred from the USN to the RNN they had undergone an extensive modernization known as Greater Underwater Propulsion Power Program (GUPPY).

[3] The batteries had a capacity of 10.500 Ah and allowed the Walrus class submarines to operate solely on electric power for 5 hours.

[14] In the early 1960s the Walrus class submarines patrolled the waters in Dutch New Guinea and were stationed at Manokwari and Biak.