Koreans have always spoke Korean, I understand that many people think that this language was created but it has been around since….. no one knows. King Sejong merely wanted to create a writing method that could be learned by anyone.
Koreans used Chinese Characters for many years and to be honest it was not the same, Kind of how many English speakers try to Romanize the language, It simply does not work and I try hard to make it work but it will never be possible without a few more characters.
To answer your question, Koreans have always had the same language maybe over 10,000 years but no one knows.
Of course, he spoke in Korean, but when he wrote or wrote documents, he used Chinese characters similar in pronunciation to the meaning of such Chinese characters because there was no Korean.
When King Sejong created Hangul, many aristocrats opposed it.
The Chinese characters came to Korea around 108 B.C. At that time, the national name was Joseon, and Koreans call it Gojoseon to distinguish it from the Joseon kingdom of the same name later.
The method of using Chinese characters was called Idu, which uses Chinese characters' yin and Hun to express Korean.
In other words, it is a word that goes along with the yin and meaning of the Chinese characters.These Chinese characters were used by the aristocracy in Korean history, and most ordinary people did not know them. Since Chinese characters are hieroglyphics rather than phonetic ones, the number of characters is too large, with 36,000 such characters.
Therefore, because it was difficult to learn Chinese characters, most of the classes that knew the defects were aristocrats, including bureaucrats, and even generals were ignorant of Chinese characters because they were uncivilized.
The selection of government officials in Korean history was made by the aristocracy and the commoner class with such Chinese characters, most of which were selected by aristocrats or by commoners with aristocrats as teachers.
The reason for this is not that they know all the letters in Chinese characters, but that they put the books of famous philosophers and intellectuals in Chinese characters as a test question.
Therefore, they usually had to study for 20 to 30 years if it was short or 10 years long.
Therefore, in the old days when it was difficult to make ends meet, it was difficult to get ahead in the world by learning Chinese characters, taking tests, and being selected as a government official. So naturally, the aristocracy took up many government posts, and the common people became part of it. History glorifies the creation of Hangeul by King Sejong, but my personal thoughts differ slightly.
Historically, it is difficult to create an easy-to-learn article for the people. Therefore, we should consider the historical background of King Sejong's creation of Hangeul. The political system of the Joseon Dynasty was different from the previous political system.
During the Joseon Dynasty, there was a system called Uijeongbu. Uijeongbu is the same as the current parliamentary system. There were three officials from each department at the top of the list. When the king made a decision, the king could give orders only when he and the government were in agreement. Thus the king's authority was weakened and the authority of management was strengthened.
No matter what order the king was going to make, when the opposition from Uijeongbu became impossible, King Sejong, the smart king, thought of strengthening his royal authority.
It is the people's support that is the power of any country. For example, the king ordered the land to be distributed for the people. King was making a public announcement to inform the Guards of these orders. If all the people are aware of the writing, the king's will is conveyed to the people, but if the people are not aware, serious problems arise.
When the king asked the nobles who knew the writing what it was about, even if it was a good meaning to give the land to the people who didn't know the writing...If the order is against the nobles, the aristocrats would say, "The king does unnecessary things again," and all the people would find the king doing unnecessary things.
However, if anyone has easy reading and writing, the people read the contents of the notice without asking the nobles and find out that the king works for them. So many aristocrats opposed making Hangeul, and even after making Hangeul, they faced a lot of opposition.
King Sejong made many books in Korean, but Hangeul was not used in the national affairs, and it spread throughout the years through novels, and all Koreans used Hangul like Hanjae.
By the dynasty of Koryo (918–1932), definitely yes. Before that, the evidences are too scant to discuss.
Written evidence of Korean language before the invention of Hangeul in 1443 (this year is the suggested year of actual invention, and 1446 is the year of its official publication) are, honestly, very scant, and often very hard to decipher because Koreans employed a tactic somewhat similar to modern Japanese to write their own language with Chinese logosyllabary. During the dynasty of Koryo, there are some written records of the contemporary language spoken in Korean peninsula. The wordlist clearly shows that the language is Koreanic.
There are no surviving books made before the ‘Samguk Sagi’ (11th century) in Korea, and almost all of the engraved texts are written in Classical Chinese, so studying about Korean language before the dynasty of Koryo is very tough.
Before the unification of Korea in 660s, it is not sure if the languages of rival polities (namely, Goguryeo, Baekje, Silla, and Gaya) were close to each other or not. ‘Samguk Sagi’ and other books made during Koryo dynasty contains some Korean texts mainly coming from Silla (the victor), and those seems Koreanic, but information about the other lost polities are very scant.
Most scholars don’t give a question about those records about Silla, because multiple sources are all showing that some Koreanic language which is related to the language of Koryo was spoken in the kingdom of Silla. And simply, considering the continuity of Silla - Koryo - Joseon dynasties ruling the same region, there is no reason to suspect a harsh language switch there. The existence of so called ‘Old Korean’ (the language spoken in Silla) seems safe to claim.
Before the unification by Silla in 660s, for the most of the time being, Silla could control only a small corner of the peninsula, being the weakest polity before the 6th century. Before that period, Goguryeo, Baekje, and Gaya were rampant, but their languages are little known. Some records claim that they all spoke closely enough to Silla so that there were no need of serious interpretation, but there are strong political motives (unification of Korea) to falsely claim that. Some scholars, based on some word evidence, claim otherwise.
‘Buyeo-Japonic hypothesis’ (I forgot the exact name of the hypothesis, sorry), claims that Goguryeo, Baekje and Japan belong to same language family, contrary to ‘Three Han tribes’ (its identity is dubious, but it always includes Silla), which are the ancestors of Koreanic-speaking people.
In the kingdom of Baekje, the legend claims that the ruling class came from ancient Buyeo tribal kingdom (which is also an ancestor group of Goguryeo), while the peasants were among those ‘Three Han’ tribes. And there is a record that the ruling class and the peasants of Baekje called their king with different name, which may be a clue that those two classes spoke different languages. But again, these claims are based on only scant and dubious evidence.
Speaking of Gaya, it’s more problematic because the matter is now a politically sensitive matter between Korea and Japan. People of Gaya are supposed to be one of those ‘Three Han tribes’ which also includes the people of Silla. But the problem is, the ancient tribal confederation of Gaya seems to be somehow related to ancient Japan.
It must be ‘under heavy cultural influence from Japan’ at least (based on archaeological excavations), if not Japonic at all. Written history of early Silla (as in ‘Samguk Sagi’) is full of ‘resistance against Japanese hegemony’, which is quite doubtful considering the distance between Yamato government of Japan and Korea, so it makes us suspect some Japonic powers around the southwest of Silla or at least in Kyushu in Japan. But again, the situation like ‘Koreanic people in Gaya under suzerain of Japan’ is not an impossible scenario. Language situation of Gaya maybe not so related to its Japan-like culture or political structure. Again, there are too scant evidence.
Spoken language cannot just pop up at any specific time in a culture. Koreans were speaking Korean spoken language 한국말 for all those long years in our history. 5,000 years of record.
If you can read Classical Chinese, this will help you understand. Check the first sentence - Since our spoken language is different from that of China, writing and speaking doesn match…
The fact that Koreans speaking our language means it was spoken in this land for thousands of years like other languages in the world.