For 10 points, name this peninsula split into a northern half ruled by Kim Jong-Il and a southern half with capital Seoul.
The Silla dynasty ruled in this country where Sejon the Great was an early ruler of the Choson Dynasty. A foreign invasion of it by Toyotomi Hideyoshi lost at the battle of Noryang with the help of this country's turtle ships. One war in this country featured a landing by Douglas Macarthur at Inchon, which led to its 38th-parallel demilitarized zone. For 10 points, name this peninsula split into a northern half ruled by Kim Jong-Il and a southern half with capital Seoul.
The Silla dynasty ruled in this country where Sejon the Great was an early ruler of the Choson Dynasty.
{Korean} Peninsula [accept {Hanguk}; accept {Choson} before mentioned]