Why did the Presbyterian Church of Korea split in 1959?

I realise you asked this question five years ago, and an answer may no longer be needed, but I was curious, so here is a summary of what I found, starting with an introduction:

The Presbyterian Church of Korea (PCK) is based in Seoul, South Korea. However, its inception took place in Hwanghae Province, current North Korea. There, Sang-Ryun Suh founded the first Protestant church of Korea, the Sorae Church in 1884... Soon after the liberation from Japanese Occupation, the General Assembly experienced divisions of the “Koshin” group in 1951, “Kijang” group in 1953 and the “Hapdong” group in 1959 due to issues such as the forced Japanese shrine worship and related theological disputes, and the General Assembly re-identified itself since then with the current name, “The Presbyterian Church of Korea”, as the “Tonghap” group. Source: https://www.cwmission.org/member-church-feature-presbyterian-church-of-korea-pck/

From there I found a paper entitled ‘Unity and catholicity in the Korean Presbyterian Church: An ecumenical Reformed assessment’ which delves into the history of the PCK and the disunity that resulted in three major schisms (1952, 1953 and 1959). These schisms arose after the Japanese annexation (1910-1945), and during and after the Korean Civil War (1950-1953).

I will partially quote from the paper, in the hope that is allowed. I went to the “How to cite this article” link, but couldn’t understand what I was supposed to do, so here is the link to the paper that I refer to: http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2074-77052016000100032

One socio-political factor that played an important role in the disunity in the PCK was the Japanese annexation of Korea in 1910 and subsequent forced Shinto worship, with a meticulous plan. Regardless of opposition by most pastors of the PCK, Japan finally compelled the PCK to practise Shinto worship.

One element of conflict in the PCK at that time was theological education. After the closure of the Presbyterian Theological Seminary in 1938 due to Shintoism, the Chosun Theological Seminary was founded in 1940 by Korean pastors who did not take Shintoism seriously, but actively helped the Japanese policy and were theologically liberal, denying the infallibility of the Bible in the conservatives' eyes. After liberation the Chosun Seminary was the only theological seminary and was approved by the GA in 1946. An example that reflects the seriousness of liberal theology in the Chosun Seminary was an incident where 51 students opposed its liberal teaching and appealed to the GA. As a result of that incident, Pastor Han Sang Dong, who was a central figure among the released pastors and their followers, opened a new theological seminary, the Korea Theological Seminary, in the hope of restoring and purifying the PCK through teaching pastoral candidates conservative orthodox theology.

In 1959 the PCK experienced a devastating schism that tore it into two halves of almost the same size, between the party advocating for the World Council of Churches (WCC) and the anti-WCC (or National Association of Evangelicals) party. This schism began with an illegal and morally shameful incident involving a most influential theologian, the principal of the GA (Chonghoi) Presbyterian Theological Seminary, Park Hyung Ryong. Park's followers (of the anti-WCC party) thought of his collapse as their political collapse in the power struggles of the PCK. At that time, the membership of the WCC became an item on the agenda of the GA meeting. The anti-WCC party criticised the WCC and attacked the WCC party by raising questions about its theological liberalism and support of communists and guerrillas. The WCC party regarded the attack of the anti-WCC party as a strategy to escape from its crisis and to maintain its political hegemony in the PCK. This conflict, regardless of attempts at reconciliation, led to a tragic split in the end. The WCC party was called the Tong Hap Church and the anti-WCC party was called the Hap Dong Church.

The fourth schism happened in 1979 in the Hap Dong Church between the mainline GA party and the non-mainline parties. The situation was very complicated and it is difficult to describe it clearly, because a number of parties have come into being since 1979. Not only pastors in the GA, but also professors and students in the theological seminary complained of the secularisation and corruption of the GA leaders and the illegality of the board of directors of the theological seminary. They requested that the leaders of the GA and theological seminary practise purification.

The paper continues with a section on the analysis and assessment of the disunity in the Presbyterian Church in Korea. I hope you will find the information useful, even though it is five years late!