Passage: Goguryeo (고구려; 高句麗; [ko.ɡu.ɾjʌ], 37 BCE–668 CE), also called Goryeo (고려; 高麗; [ko.ɾjʌ]), was a Korean kingdom located in the northern and central parts of the Korean Peninsula and the southern and central parts of Manchuria. At its peak of power, Goguryeo controlled most of the Korean peninsula, large parts of Manchuria and parts of the Russian Far East and eastern Mongolia.Along with Baekje and Silla, Goguryeo was one of the Three Kingdoms of Korea. It was an active participant in the power struggle for control of the Korean peninsula and was also associated with the foreign affairs of neighboring polities in China and Japan.

Question: What are was the conflict over?
control of the Korean peninsula