According to "Koraishi," in 1272, Crown Prince Sim of Goryeo (later King Chungnyeol) gave his opinion to Emperor Kublai of the Yuan Dynasty, "I think that Japan has not yet leant the virtues of the Emperor. Therefore, an imperial order should be issued to use the army, warships and provisions for this purpose. If you commission your vassals to do it, we will do our best to support the imperial army."
『高麗史』によると1272年に、高麗の王世子の諶（しん、後の忠烈王）が、元(王朝)のクビライ皇帝に「惟んみるに、日本は未だに聖化を蒙らず。故に詔使を発し、軍容を継耀かし、戦艦兵糧まさに、須いる所あらん、もし此事を以って臣に委ねなば、勉めて心力を尽くして　小しく王師を助くるに庶幾（ちか）からん」と具申したとある。