Kublai, who in 1260 became the fifth emperor (Khan) of the Mongol Empire that was later called 'Yuan' (the Great Yuan Ulus, Great Yuan Dynasty or Yuan Dynasty), in 1266 planned to send the first envoys to establish diplomatic relations with Japan, through Goryeo in the Korean peninsula, which had already become its subject, while starting to conquer the Southern Sung Dynasty in 1268, which had been its long-standing aim since the reign of the second emperor Ogodei.
1260年にモンゴル帝国の第5代皇帝（ハーン、ハーン）に即位した後のいわゆる「元(王朝)」（大元ウルス、大元朝、元朝）の皇帝クビライは、1268年（日本の文永5年・大元朝の至元(元世祖)5年）に第2代皇帝オゴデイ以来の懸案であった南宋攻略を開始する一方、既に服属していた朝鮮半島の高麗を通じて、1266年に日本に初めて通交を求める使者を送ろうとしていた。