Kuruwa Walls were a specific type of Castle Support Fortification, developed in Feudal Japan around the 10th Century AD. The type and it's subsequent variations, would continue throughout most of Japanese Medieval History. The Kuruwa System is akin to a more open (modified) European ''Motte and Bailey'' form. Made from sea shell and sand (hardened), these Walls were used to surround Castles, Military Structure and later Homes of Nobility (for protection).
Heights varied from several feet to 8-feet. Likewise depth varies, but typically several feet were applied. Although seen in later Centuries, steps and footholds (for soldiers), were not added (as in European versions). The same is applied to Defensive Towers, which could also have Kuruwa applied.
Three primary designs were employed from the 10th Century to the 15th Century. The first was a ''Box'' style, and the most similar to The Motte and Bailey System. These Kuruwa Walls were used to secure a large perimeter (square shaped). In the Center of this ''fortification'' was another smaller Kuruwa Wall (also Square). Into this a smaller Castle of Manor House was constructed. The second version, also used a large perimeter ''Box'' – but the smaller structure was place outside the primary Square (but attached). This was ideal for Military Storage or Training Facilities. Equestrian stabling was also used with this format. The final was similar to the 2nd, only in that the Outer Square was placed inside (still adjoining. This was ideal for Manor Houses. Many example of Medieval Kuruwa Walls have survived today.