Sogamae (outer citadel) (総構え)

The sogamae is a castle or fort's outer enclosure or the area that the enclosure surrounds. In addition to the castle itself, the term refers to the entire Japanese castle structure surrounding the castle town with the outer wall, moat or Dorui (earthwork). The word "soguruwa" is also used.

Summary
Unlike in Continental Asai, walled towns did not develop in Japan with only a few exceptions partly because different races seldom invaded Japan and partly because most of the land is covered with mountains; 'Josaku' (official defense sites) constructed as military defense facilities and 'Yakata', or worriers' residences armed with moats and wooden framed stages, developed into mountain castles during the Middle Ages.

As castles developed up until the early modern period from being simply military installations to serving as political centers of government, defensive lines were constructed further outside to take over the role of those functional components (inner castle) that had previously served to defend the castle town and retainers. This is the sogamae.

The word "castle"usually means the inner castle, while the precise boundaries of the sogamae, the outer castle, were unclear since they included natural geographical features (mountains and rivers). Moats (hori) of the sogamae was called "sohori"and frequently it also called the "outer moat" as well. However, when the term, outer moat, was simply used, this might refer to the sogamae moat itself or the outward moat of the castle.

The sogamae of Odawara Castle, stronghold of the Late Hojo clan, is extremely large with the castle town surrounded by an approximately 9km long dry moat and an embankment. The outer enclosure of Osaka Castle also measured approximately 9km in length and during the Siege of Osaka, the Demaru (Sanadamaru) branch castle was built outside of the south gate of the outer wall; it is said that the Demaru prevented the Tokugawa forces from coming within the outer wall at all. During the Edo period, Edo Castle had the largest outer enclosure, and the spiral arrangement of its moat, stone wall and fence contained the whole of Edo city.

A typical sogamae could be considered to be a moat and wall that encloses an entire city as can be seen in Chinese castles and medieval European cities. The medieval city of Sakai was prepared for defense by being surrounded by a moat 3m deep and 10m wide on three sides and a wooden door. "Odoi," earthworks for defence and potection from a flood, in Kyoto was also an archetypal sogamae with a total length of 22.4km and its structural remnants can be seen.

The Oldest Remains
The ruin of the Itami Castle in Itami City, Hyogo Prefecture, has been determined to be the oldest sogamae remain in Japan, and is a nationally designated historic site. The Arioka Castle was named the Itami Castle since it was constructed by the Itami clan during the period of the Northern and Southern Courts (Japan) but Murashige ARAKI had the structure renovated, a sogamae constructed, and the name of the castle was changed into the Arioka Castle during the Tensho era (1573-1592). However, the castle was abandoned 10 years later.