“Hamamatsu Castle,” the foundation of Tokugawa Ieyasu’s path to becoming the ruler of Japan

Introduction

In the 2023 historical drama series “What Will You Do, Ieyasu?”, Matsumoto Jun has been chosen to portray the protagonist, Tokugawa Ieyasu. Ieyasu made significant efforts in the fortification and expansion of Hamamatsu Castle. This article provides an explanation of the Shusei Castle that bears the 300-year history of the Tokugawa clan, renowned for its nomen-zumi stone stacking technique.

Skillful incorporation of Takeda’s castle construction techniques and numerous renovations

The “Hikuma-juku” designated by Ieyasu as the center of control over Totomi Province was a bustling commercial hub that rivaled the capital and Mitsuke, serving as a prominent commercial base within the Hamamatsu territory and post town on the Tokaido Road.

The original Hikuma Castle was built on hilly terrain overlooking the Tokaido Road. It is now collectively referred to as the “Kojo” (Old Castle), consisting of square-shaped baileys enclosed by earthen embankments. The outer perimeter of the Kojo was surrounded by a moat. Edo-period maps depict three entrances called “Myokoji-guchi” to the west, “Shimodare-guchi” to the southeast, and “Genmoku-guchi” to the north. The remains of the Kojo are still located on the highest ground in the surrounding area, confirming its position on the hill.

During the Sengoku period, the Tenryu River had two branches, the Otenryu and the Shotenryu, with the smaller Shotenryu in the West flowing around the current Magome River area. Consequently, Hikuma Castle was situated in a strategic location with a natural moat formed by the Shotenryu to the west and steep cliffs leading to Saigagake to the north, while low-lying wetlands spread from east to south. Upon arriving in this area, Ieyasu relocated the central area of Hikuma Castle to the hilly region on the opposite bank, further expanding it to the south and incorporating the former Hikuma Castle as an eastern defense.

After the year 1572, Takeda Shingen and Katsuyori repeatedly invaded the province of Totomi. It seems that Ieyasu gradually expanded Hamamatsu Castle during breaks in the battles. However, significant renovations began in the 5th year of the Tensho era (1577) after forcing the Takeda forces to retreat from northern Totomi and isolating Takatenjin Castle. From February of the 6th year of Tensho (1578) onwards, various records mention the construction work at Hamamatsu Castle. It was during this time that the construction of the “Sakuza Kuruwa,” located on the northwest bank across the moat from the central area, took place, revealing the expansion of Hamamatsu Castle.

During this period, the castle-building techniques of the Tokugawa clan advanced rapidly. The main reason for this progress was the incorporation of the Takeda clan’s castle-building techniques through the acquisition of their castles in Totomi. Among them, the most significant change was the introduction of “yokobori” (lateral moats). It allowed for the incorporation of the northern “Sakuza Kuruwa” and the southern “Demaru,” expanding the width of the moat surrounding the central area and successfully enhancing the defensive structure. This established the castle’s appearance as a residence. The Tokugawa clan skillfully adopted and improved the Takeda clan’s castle-building techniques until around the 9th year of Tensho (1581). By this time, even under Oda rule, influential vassals were constructing advanced castles with tiled keeps and stone walls, rendering earthen castles outdated. However, the Tokugawa family had not yet fully grasped the group of skilled craftsmen and was not at the stage of constructing stone walls and tiled buildings. The introduction of “ishigaki fushin” (stone wall construction) at Ieyasu’s residence would have to wait until the construction of Sunpu Castle.

Author:Kato Masahumi

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