The origin of soju dates back to the 13th century Goryeo, when the Levantine distilling technique was introduced to the Korean Peninsula during the Mongol invasions of Korea (1231–1259), by the Yuan Mongols who had acquired the technique of distilling arak from the Persians during their invasions of the Levant, Anatolia, and Persia. The distilleries were set up around the city of Gaegyeong, the then capital (current Kaesong).
Soju is traditionally made by distilling alcohol from fermented grains. The rice wine for distilled soju is usually fermented for about 15 days, and the distillation process involves boiling the filtered, mature rice wine in a sot (cauldron) topped with soju gori (two-storied distilling appliance with a pipe). In the 1920s, over 3,200 soju breweries existed throughout the Korean Peninsula.
Soju referred to a distilled beverage with 35% ABV until 1965, when diluted soju with 30% ABV appeared with South Korean government's prohibition of the traditional distillation of soju from rice, in order to alleviate rice shortages. Instead, soju was created using highly distilled ethanol (95% ABV) from sweet potatoes and tapioca, which was mixed with flavorings, and sweeteners, and water. The end products are marketed under a variety of soju brand names. A single supplier (Korea Ethanol Supplies Company) sells ethanol to all soju producers in South Korea. Until the late 1980s, saccharin was the most popular sweetener used by the industry, but it has since been replaced by stevioside.
Soju ilianzishwa katika karne ya 13 na ilitengenezwa katika karne ya 13 na watu wa Korea wa Yuan ambao walipata mbinu ya distillation ya Arak kutoka kwa Waajemi wakati wa uvamizi wao wa Levant, Anatolia na Persia. Viwanda hivyo vilijengwa karibu na jiji la Gaegyeong, lililokuwa mji mkuu wakati huo (sasa Kaesong). Kwa kawaida soju hutengenezwa kwa kutengeneza pombe kutoka kwa nafaka zilizochemshwa. Mvinyo wa mchele kwa soju ya distilled kwa kawaida huchemshwa kwa siku 15 hivi, na mchakato wa distillation unahusisha kuchemsha divai ya mchele iliyochujwa, iliyokomaa katika sot (soto) iliyofunikwa na soju gori (kifaa cha distillation cha ghorofa mbili na bomba). Katika miaka ya 1920, kulikuwa na viwanda zaidi ya 3,200 vya kutengeneza bia ya soju katika Peninsula ya Korea. Soju ilikuwa kinywaji cha kawaida cha soju iliyopunguzwa kwa 30% ABV hadi 1965 wakati serikali ya Korea Kusini ilipopiga marufuku destili ya jadi ya soju kutoka kwa mchele ili kupunguza upungufu wa mchele. Soju ni ethanol iliyotengenezwa kwa kutumia ethanol iliyotengenezwa kwa kiwango cha juu (95% ABV) kutoka kwa viazi tamu na tapioca, ambayo ilichanganywa na ladha, na vinywaji, na maji. Bidhaa za mwisho huuzwa chini ya majina mbalimbali ya bidhaa za soju. Mtoaji mmoja (Korea Ethanol Supplies Company) huuza ethanol kwa wazalishaji wote wa soju nchini Korea Kusini. Kufikia mwishoni mwa miaka ya 1980, saccharin ilikuwa tamu maarufu zaidi iliyotumiwa na viwanda, lakini tangu wakati huo imebadilishwa na stevioside.