Umadashi were an effective defensive barrier and compound complex built in front of castle gates, outside of the main moats, and used as a screen to facilitate cavalry charges and attacks during times of siege. Like a barbican gate system, the Umadashi worked like an airlock for a castle, allowing attack parties to sally forth and safely return, without letting the enemy in. They served as a first line of defense, protecting the main gates, although the umadashi did not always have gates or wooden doors protecting their entrances.
Details of a simple Umadashi
Umadashi vary in size from small earthen walled sections, to huge moat surrounded stone and earth embankments with turrets and walls. Most Umadashi featured a water, or dry moat out front.
The most basic type consist of a simple straight earthen embankment with no moat, or curved inwards at the end making a partial enclosure in front of the castle gate. Semicircular, square shaped, even intersecting Umadashi can be found.
Detail from a castle design book with an Umadashi guarding the front gate
Larger Umadashi were called Umadashi Kuruwa (Kuruwa being the old name for Maru, or bailey) while an independent Umadashi Kuruwa was called a Dekuruwa, or Demaru. The Sanada-maru of Osaka Castle was one such Demaru, or Dejiro, “outer castle”.
The biggest examples of Umadashi were employed at Nagoya, Sasayama Castle and Hiroshima castles.
Detail of Sasayama Castle showing three large Umadashi
Sasayama Castle Umadasgi georama
Unfortunately, at the end of the Edo period, Umadashi were among the first castle features destroyed, and very few remain. Some of the best remaining examples can be found at Sasayama Castle (Hyogo Pref.), Odawara Castle (Kanagawa Pref) and Suwahara Castle (Shizuoka Pref).