Castles of the Sengoku Period

Most Sengoku campaigns were about castles. Field battles were rare, risky and often indecisive; taking or holding a fortress determined who controlled the land, the roads and the tax revenue around it.

Japanese castles of this era look nothing like the popular image of a white tower on a stone base — that came late, and most of the famous survivors were built or rebuilt after the wars ended.

From mountain fort to castle town

The typical early Sengoku castle was a yamajiro, a mountain fortress: a hilltop cut into terraces, with earthen ramparts, dry ditches, wooden palisades and simple buildings. It was defensible and almost impossible to live in or govern from.

From the 1570s the pattern changed. Oda Nobunaga's Azuchi Castle, built on Lake Biwa, put a tall decorated keep on a stone base in a location chosen for commerce and communication rather than for defence. The castle became a seat of government and a statement of power.

Around it grew the castle town, where merchants and artisans were concentrated and taxed. Most major Japanese cities today — Nagoya, Kanazawa, Sendai, Hiroshima, Osaka, Tokyo — began as or grew from a Sengoku castle town.

How castles were attacked

Direct assault was expensive. The methods that appear repeatedly in the record are:

• Encirclement and starvation — the most common approach, used at Odawara Campaign in 1590 with an army of 200,000.
• Water attack — damming a river to flood the fortress, as Kuroda Kanbei planned at Takamatsu in 1582.
• Bribery and defection — buying a gate open, which decided more sieges than any weapon.
• Fire and infiltration — work usually given to shinobi.
• Artillery — rare, but decisive at the Siege of Osaka in 1614, where cannon fire into the inner keep helped force a truce.

Castles that decided the wars

Odawara — the Hojo fortress that enclosed an entire town within its outer defences, and held out against Uesugi Kenshin and Takeda Shingen before falling to Hideyoshi in 1590.

Ueda — a small castle in Shinano where Sanada Masayuki beat Tokugawa armies twice, the second time delaying the Tokugawa heir past Battle of Sekigahara.

Osaka — Hideyoshi's great fortress, built on the site of a fortified temple complex that had resisted Nobunaga for ten years, and destroyed in 1615.

Nagashino — a small castle whose garrison held long enough for a relief army to arrive and destroy the Takeda. See Battle of Nagashino.

What you can still see

Only twelve Japanese castles retain an original main keep built before the modern era. The ones with the strongest connection to the people on this site are Hikone, built by the family of Ii Naomasa, and Matsumoto in the former Shinano Province. Himeji, the most famous surviving castle, reached its present form under a Tokugawa lord after the wars.

Most other famous keeps — Osaka, Nagoya, Kumamoto — are twentieth-century reconstructions on original stone foundations. The foundations, moats and earthworks are usually the genuinely old part, and often the more interesting one.

Many Sengoku sites have no buildings at all. The mountain-fort sites at Kasugayama, held by Uesugi Kenshin, and Tsutsujigasaki, the Takeda residence in Kai, are earthworks and stone bases, and reward a visit if you know what you are looking at.