The phrase was quoted from a part written about the attack/withdrawal of an army in the battle section in "Sonshi" (Chinese books about tactics) which says ''as fast as the wind, as quiet as the forest, as daring as fire, as hard to know as dark, as immovable as the mountain, and the movement is like pealing thunder.'
「疾如風、徐如林、侵掠如火、不動如山」の句は『孫子(書物)』・軍争篇で軍隊の進退について書いた部分にある「其疾如風、其徐如林、侵掠如火、難知如陰、不動如山、動如雷霆。/其の疾きこと風の如く、其の徐（しず）かなること林の如く、侵し掠めること火の如く、知りがたきこと陰の如く、動かざること山の如し、動くこと雷霆（らいてい）の如し」からの引用。