koreanhistory1-5, Exercise 2: Khitans and Mongols (a sample; yours will differ)

Model answer:

1. [Source] Against the Khitans (993, 1010, 1018) Goryeo fought and negotiated; the 1018 campaign ended with a win at Kusong, the 1022 peace formalised vassalage, and a wall (Cheolli Jangseong) was built from 1033 to 1044.
2. [Source] Against the Mongols (1231 to 1259) the court moved to Ganghwa Island (1232), which was never taken, while provincial people were told to take refuge in citadels or islands; peace came in spring 1259, and Goryeo became a Yuan client state with marriage alliances.
3. [Source] Hedged figures: the Khitan troop numbers (a claimed 400,000; 100,000; 208,000 reported) and the Mongol-era "estimated 206,800 captives"; the number of invasions is nine in one article and six in another.
4. [My own reading] Both wars ended in a settlement that left Goryeo in place as a vassal, so the sources' later question of how to describe the outcome ("victory" or "vassalage") depends on what is being measured.