How did Koreans write their language before Hangul was created?

Before the invention of Hangul in the mid-15th century, Koreans primarily used Classical Chinese for writing. Because the Korean upper classes were bilingual—speaking Korean but writing in Chinese—early literary activity and official records were conducted using Chinese characters.12

To bridge the gap between the Chinese script and the Korean language, several transcription systems were developed:

• Idu: Devised by the 7th century, this system used Chinese characters to create rough transliterations of Korean texts, often employing characters for their phonetic value to represent Korean grammatical particles and inflectional endings.1
• Hyangch’al: An extension of the idu system that allowed for the transcription of entire Korean sentences using Chinese characters.1
• Kugyŏl: A system where abridged versions of Chinese characters were inserted into texts to denote grammatical elements.1

Despite these innovations, the use of Chinese characters remained dominant among scholars and the elite for centuries, even after the creation of the native alphabet.312