Because Yokoyama-jo Castle was located in Sekigahara of Mino Province (the present-day Sekigahara-cho, in Gifu Prefecture) and near the Hokuriku-wakiokan road running through the west side of the base of the Azai clan, Odani-jo Castle (in Kohoku-cho, Shiga Prefecture), and located only six or seven kilometers from Odani-jo Castle, Nobunaga ODA attempted to capture Yokoyama-jo Castle as an important front-line base.
横山城は美濃国の関ヶ原（岐阜県関ケ原町）から浅井氏の本拠地である小谷城（滋賀県湖北町）の西側を通る北陸脇往還街道のすぐ脇に立地するうえに、小谷城から6-7kmほどの距離しかないため、織田信長は重要な前線基地として横山城の攻略を目指した。