Korea has had an extremely long history, so long that the Korean language, no doubt has changed a lot with time, but Korean has mostly been the language of the Koreans, except for a few exceptions. The answer to this question needs a short history and linguistic history of Korea.
The known history of Korea goes back so far it is amazing! The very first emperor of Korea was a son of a man from the Tower of Babel. They call him a son of God. Korea was originally called Gogureyo. Gogureyo was the major power of the old eastern world. They were not just on the Korean peninsula back then. They reached up off the peninsula, into Manchuria, into a large part of China, into Mongolia, and even into parts of Russia. The language they spoke was an old form of Korean. There are still people living in China who speak an old form of Korean at home, but speak Mandarin Chinese or some other form of Chinese out of the home. Korea has always had just one first language, Korean, but the Chinese don’t speak just Chinese in China. In China, they speak all different kinds of languages. It is not as linguistically united as many people think. There are more than 12 languages spoken in China. Some of the Chinese even speak a form of Arabic. If you go up to Mongolia now a days which is not China, their language is extremely like Korean. Korean and Mongolian are so similar that I knew a Mongolian girl in Korea who seemed to learn Korean overnight. She found Korean easy. I also knew a Chinese girl in Korea whose family spoke an old form of Korean at home, but a form of Chinese out of the home, and she came to Korea to study thinking it might be easier to study in her first language because she had to do all her studying in China in a form of Chinese. She is actually the first person I had a conversation with in Korean because she really pushed for me to speak Korean. She was 100% Chinese, but she still carried the language of her ancient ancestors, Korean.
There was a time during the time of Gogureyo that lasted about 5,000 years, that there was a group that came from China into Korea looking to set up a utopia. A Chinese noble the Koreans call “the Archer” became very disgusted with China and China’s politics. They gathered other Chinese noblemen who were scholars, doctors, lawyer, holy men, philosophers, builders, etc., and a large group of them all headed for Korea to set up a utopia. Korea has always loved anything or anyone that was a civilizing influence on their society. They accepted this group of people from China with open arms. The Koreans went about learning whatever they could from these noblemen, and the noblemen wanting to set up a utopian society were happy to teach them. Korea liked their leader they called “the Archer” so much that they made him the emperor. If the Korean nobility ever spoke Chinese, this would be the closest, but these Chinese melded into the Korean society and became Korean. The capital of Gogureyo was in North Korea.
After about 5,000 years of Gogureyo, Korea ended up splitting into three different countries. The different countries were called Shilla, Goreyo, and Bekjae. Shilla’s capital was at Seoul, and that is when Seoul was first built. Bekjae’s capital was at Busan. Goreyo’s capital was furtherer north, in Manchuria, if my memory serves me correctly. All these countries spoke the old form of Korean. You must realize that all languages change with time. I am not quite sure at what period what the world calls the Chinese characters were invented, but probably during Gogureyo because all three of these Korean countries were using Chinese characters during this time. The Chinese characters were actually invented by old Korea, and not China as people suppose. The Bekjae Kingdom was the closest to Japan, and they were also in parts of China. However, since Bekjae’s capital was at Busan, they were closer to Japan than any of the other of the three kingdoms. They shared what they were calling Hanmoon with the Japanese, and the Japanese translated the word Hanmoon into Japanese, and in Japanese, Hanmoon became called Kanji. Kanji literally translated into English is “Han letters.” In Korea, “Han” means “one,” and Korea’s name for itself is Hangook, or one country. The Han river flows through Seoul, and they call God Hananim which means “The one respected Lord” They have known about him since the beginning of Goguryeo because the father of their first emperor, as I said, came from the Tower of Babel. Anyway, all three of the old kingdoms f Korea spoke Korean. Eventually, the people of Shilla decided that they wanted to unite the Korean people again and actually be Hangook, which literally means one country. They ended up conquering the other two, Goreyo and Bekjae, and they began calling themselves Hangook.
Pronunciation in Korea has changed with time and also changes according to which region you live in in Korea. One of the big things that tells you that is the name the countries who are not Korean call Korea. In Korean, they have a letter: ㄱ. This letter is at times pronounced as a “g,” and at times pronounced as a “k.” They actually have the hard “k” sound in Korean with this letter: ㅋ. However, the name “Korea” came about because the people of Gogureyo used to travel the old Silk Road, the trading route that connected Europe and Asia in ancient times. The people on the old Silk Road heard the ancient Koreans say their county was “Gogureyo” and ended up calling their country “Korea” from what they heard. I encountered the same phenomena with the letter ㄱ. If you go to a subway station in Korea, on the wall of the subway, they have the Korean word for subway: 역 transliterated on signs into English as “yok.” In some places in Korea, they say “yok.” However, in Hwagok, they don’t. In fact, if you say “Hwagok Yok” to a taxi cab driver in Hwagok, they don’t understand. You must pronounce it “Hwagong yong.” There are another 2 letters I know have also changed pronunciation: 에 and 애. The Koreans say at one time, there was a different between the pronunciation of these two letters, but the modern Korean doesn’t know the difference anymore, and they are both pronounced like a short “e” sound in English.
There was a lot of fighting in the east in ancient times, and Korea (Hangook) kept trying to stay out of it, but finding it hard. The people from Mongolia were driving both China and old Hangook, old Korea, crazy. The Koreans had lost territory because of the three kingdom’s period which means there had been fighting among the Koreans themselves. The capital of Hangook became Seoul, the city that was built by the Koreans of the Shilla kingdom as their capital. (Seoul is one of the oldest cities in the world.) Korea found themselves wedged in between China and Japan who were both becoming more and more powerful and both becoming a pain in the neck. The people of Mongolia were making war on everyone, even the Europeans. Art one point, the Mongolians were close to ruling all of Europe. I visited a war museum in Korea that had a whole section dedicated to telling how they fought off the Mongolians.
Korea had shrunk, but they still had the Korean peninsula and Manchuria at this point. China and Japan were overbearing problems. The Koreans built their homes high up on mountain tops and then put many stairs up to the actual entrance of the house. They did this because China was constantly invading. Their strategy was that when the Chinese came, they would have to climb the mountain, and then climb the stairs, and by the time they got to the top, the Chinese would be out of breath, but the Koreans in the home wouldn’t be out of breath, and it gave the Koreans an advantage. Korea is the most mountainous country in the world, so it worked. Those mountains are part of the reason Korea was able to remain Korea and not be absorbed into China as many of the other countries in the east were.
The other problem the Koreans had was Japan. At one point, Japan became completely united under a shogun named Hideyoshi Toyotomi who lived in the castle in Osaka. It was actually the first time all of Japan was unified. After Hideyoshi Toyotomi united all of Japan, he decided to incorporate Korea into Japan too. They were the closest country, and when Bekjae fell, their royal family had gone into Japan. People from the Bekjae royal family married into the Japanese royal family, and the current emperor of Japan has finally told everyone that he is part Korean. Anyway Hideyoshi Toyotomi was able to unite all of Japan, but the Koreans had built a think called the Turtle boat, and with the Turtle boat, the successful kept the Japanese out of Korea that time. The Japanese became a constant pest to Korea trying to incorporate Korea into Japan. They used to come and steal artisans from Korea, take them to Japan, and force them to make pottery for Japan because the Japanese didn’t have the art down like the Koreans did back then.
It was like Korea was between two bullies, China and Japan. Korea ended up paying tribute to China in rice to try to keep them off their backs and made a deal with China to keep Japan out of Korea for the rice too.
Korea had had enough of all the fighting. They didn’t want anyone to even know they were there because they had been attacked so many times. They retreated onto the peninsula and closed their borders. By the 1700s, no one was allowed to leave Korea, and if anyone came to Korea, they weren’t allowed to leave. Korea didn’t want anyone else spreading the news of their existence because they wanted peace, and they wanted to be their own country.
Eventually, Japan was successful, and they were ruling Korea. Korea was occupied by Japan around the time of WW2. The Japanese were forcing the Koreans to learn to speak Japanese. The Koreans were not even allowed to speak Korean, but the Japanese wanted them all to speak Japanese. Japan abolished the Korean royal family and the Koreans became the slaves of the Japanese.
China hadn’t given up. They were encroaching into the north into what is now North Korea, and China had become Communist. China had had an expansionist policy for many years and wanted Korea too.
There were Koreans who wanted to become Communist and others who wanted to become Democratic. They began a Democracy movement in the courts of the Myeong dong Cathedral in Seoul close to Geongbuk Palace. The Democracy movement made a provisional government in secret outside of Korea that wasn’t very strong. They wanted to throw Japan out of Korea. There were those in the north influenced by China who wanted Communism.
Finally, the United Nations, led by the United States, went into Korea to help them. They threw the Japanese out of Korea. At that point, the Korean war began because the Chinese were in the northern part of Korea. The Korean war was not just between North Korea and South Korea, but it was also between the United Nations led by America and Communist Chinese. I met old people whose homes were occupied by Chinese soldiers. I met old people who saw battles in their streets and one even said she saw a Chinese man take a sword and hit a Korean on the head and split him in two from top to bottom with his sword. The United Nations and the South Koreans together were able to push the Chinese back, but the people in North Korea still wanted Communism. The Communist Chinese began a puppet government in North Korea which turned into a personality cult that is passed down from generation to generation, from father to son. The United Nations gave South Korea back to Koreans and the provisional Korean Democratic government that had been in hiding. The Democratic government had a few false starts, but they finally took the reigns in a good way. They were learning, and they have learned. They have a strong Democratic government now.
Korea, through time, had become just a fraction of what it was in the beginning and divided by politics. S. Korea will never go for Communism. They say they love the people in the north, but they refuse to accept their politics. The American military has kept bases in Korea to try to keep the peace and keep them from being invaded again, but the S. Korean military increasingly thinks they can handle it, and the American military bases are shrinking in S. Korea. America, unlike the other countries around Korea, never wanted to take Korea over. The S. Koreans love America for the help they have given in making S. Korea autonomous and Democratic. You can speak to old people in Korea in Japanese because they learned it under Japanese occupation. There are also people of Chinese descent in Korea, but they have forgotten Chinese and are 100% Korean now. S. Korea has taken English as its second language, and seem to be English crazy. They say, “It is a global world, so they must learn to live in it.” Part of learning to live in it is studying English to talk to people from other countries, but they have always spoken Korean, from the beginning of time, since the Tower of Babel, and will continue.