In the article of December 12 in the the "Azuma Kagami" (The Mirror of the East), the official historical material of Kamakura bakufu (Japanese feudal government headed by a shogun), the background to place shugo and jito (manager and lord of manor) in kokufu (provincial office) and shoen (manor in medieval Japan) in the various districts under the Kamakura bakufu was described as the following.
鎌倉幕府の公式史料である『吾妻鏡』11月12日(旧暦)の項では、鎌倉幕府における諸国の国府・荘園への守護・地頭の設置の経緯を次ぎのように説明している。