To sum up, the history of English language education can be divided into "two and a half" period. To many, it can be divided into three periods, but my view on this is that we are still in the second period.
The first period: 1950-1970s
Back then, English was taught in Korea essentially for military purposes. South Korea had a US military presence in its territory and therefore had to train its citizens to be competent in communication with the US army and with the US ally in case of war. The United States technically has "wartime operational control" in South Korea meaning that if a war were to break out with North Korea, the United States would be in charge of leading the war. Korean men, considered potential future soldiers, had to be good "followers" of the US army.
How is language taught for military purposes? Focus is put on a comparison between the native language, Korean, and English. No conversation in class, classes are taught in Korean and Koreans were essentially taught aspects of English grammar that they were expected to be able to translate into their language. Exam questions were in Korean, and students had to answer in English.
This method was used worldwide when training spies who were expected to translate confidential documents into their native language, or by Europeans learning Latin and Ancient Greek.
The second period: 1970s-1990s
During the 1970s the South Korean economy grew considerably and the government expected students to have "business" knowledge of English.
In language there are three aspects: Competence, performance and communicative competence.
-Competence is the ability to know what is right or wrong in a language, say knowing that "I did it" is right and that "*I it did" is wrong.
-Performance is the ability to speak a language. Most speakers of a second language, despite knowing what is right or wrong in a language, reproduce what they know in the language. Say they know that "*I it did" is wrong but they still say it.
-Communicative competence is the ability to speak a language and also to know what to say, when to say it, and what is not appropriate to say in the language's culture.
So while the first period focused exclusively on competence, the second period started focusing on performance. That is, students were put under pressure to write and speak English properly, asked tricky grammar and vocabulary questions, and were rebuked when they made mistakes.
The curriculum was essentially grammar based and test based: students were tested and heavily sanctioned if they made mistakes speaking English, thus viewed speaking English as a continuous test and thought that native speakers were actually evaluating them when they were speaking, and Koreans were obsessed with "mistakes"
The third period: 1990s-today
In 1997, the Korean government decided to bring native speakers to help students focus on "communicative competence", that is, to communicate effectively with American businessmen. Soon after, the 1997 financial crisis delayed the project, and once Korea recovered, native speakers were invited to the country.
What happened? Though the government wanted students to focus on their ability to communicate with foreigners making colloquial use of English, students and companies focused on "performance": the less you make mistakes, the better you are, regardless of whether you are actually able to converse with foreigners.
Test scores became primordial, and surprised and disillusioned English teachers ended up torn between teaching "performance" and "communicative competence". While the government keeps reiterating its idea that Koreans should focus on "communicative competence", students return to "performance". A funny example is that when Korean students are asked to hold conversations in English, they write down what they have to say first, proofread grammar mistakes, double check meaning in the dictionary, and then recite their sentence. Typical behavior of people who focus on "performance" rather than "communicative competence".
This is why I argue that Korea is still in its second period. While the Western world is learning English to improve their "communicative competence" through watching English language movies and interaction with native English speakers, Koreans have decided to remain economy oriented and to focus on making less mistakes when they speak English.