Odawara Castle Hojo stronghold and national Historic Site

Stewardship and present uses

Odawara Castle (小田原城) is developed and maintained as Odawara Castle Ruins Park within Odawara City. The site combines municipal stewardship, heritage restoration projects and community use: the park contains a municipal library and a local history museum, a shrine located on one of the kuruwa (small fortification flats), and an amusement area on another former enclosure. An NPO established in 2013, Minna de Oshiro o Tsukuru Kai, has an explicit objective of promoting a wooden restoration of the castle keep (tenshu), and Odawara City has long-running plans to restore structures to their late-Edo appearance. The castle site is designated as a National Historic Site of Japan.

Location and access

Odawara Castle occupies Jonai 6-1 in Odawara City, Kanagawa Prefecture. The castle is about a 10–15 minute walk from Odawara Station, which is served by the Tokaido Shinkansen, the JR Tokaido Line and the Odakyu Odawara Line. The castle grounds are arranged across the flatland around the present-day main enclosure and on the immediately adjacent Hachiman-yama ridge to the north-west.

What survives and how the grounds are arranged

The modern park preserves the principal flatland enclosures (honmaru, ninomaru and sannomaru) that form the core of the Edo-period castle, together with restored gates, walls and a reconstructed tenshu. The castle’s main enclosures were made into a total stone-walled form in the early Edo period: the primary sections of the castle used stone walls throughout, a contrast with many Kanto-area fortifications that relied mainly on earthen banks.

By the late Edo period the whole castle complex included roughly thirteen gates and about eight yagura (watchtowers), and three coastal gun batteries were added on the shoreline. After extensive demolition in the early Meiji years most original buildings were removed; since the mid-20th century the site has been progressively restored. Present uses include a library and local museum on one kuruwa, Hotoku Ninomiya Shrine on another, an amusement area on the Byobu-iwa ridge enclosure, and ongoing reconstruction of the former rice-storehouse enclosure, which had been used as a ballpark and later parking.

The tenshu rebuilt in 1960 is reinforced concrete rather than timber; it underwent seismic strengthening and roof and wall repairs between 2015 and 2016 and was reopened on 1 May 2016 as the present exhibition keep. The city retained visible modern alterations when the tower was first rebuilt, and the 1960 reconstruction was not a precise wooden replica of the old Edo-period tenshu.

The total enclosure and medieval defences

Odawara’s outstanding military feature under the later Hojo was its total enclosure (sogamae): a continuous ring of earthen banks and dry moats that ran for a total length of about 9 kilometres, surrounding the town from the Hachiman-yama ridge to the sea. This large outer defence predated and exceeded in scale the later concentric works seen at other famous castles, and it remained the town boundary on old maps and into the early Meiji period.

The medieval component centred on Hachiman-yama, which functioned as the castle’s inner keep (a tsume-jō). Hachiman-yama comprised a chain of enclosures running from east to west (east kuruwa, main kuruwa, west kuruwa and adjoining terraces) and was where Hojo Ujimasa is recorded as taking his position during the 1590 campaign. The Komine great trench (Komine ōhorikiri) on the western ridge is the largest surviving medieval earthwork and, together with several well-preserved stretches of outer dry moat in the north-west (Sakura-bamba and Inari-mori sectors), provides visible evidence of the pre-Edo fortifications.

Across the site many medieval earthworks survive as isolated features: large trenches, double earthen banks, shoji-style wide moats exposed by excavation, and fragmented remnants of the sogamae north-western line.

Key episodes in the castle’s history

The site has a long sequence: a late-Heian residence linked to a local samurai family was later seized by regional powers; in 1416 the Omori clan expanded its control after the Uesugi Zenshū disturbance; around 1495 Ise Moritoki (known in later histories as Hojo Soun) captured and enlarged the old fortification and, by about 1518–1519, his son established Odawara as the Hojo family’s seat. For five generations the later Hojo ruled from Odawara.

In 1561 Uesugi Kenshin advanced from Echigo and conducted a major attack on Odawara; war chronicles record very large numbers and an extended siege, though contemporary accounts also note a shorter, high-intensity encirclement. In 1569 Takeda Shingen moved into nearby provinces and staged a military demonstration against Hojo territory around Odawara. From late 1560s through the 1580s the Hojo undertook large-scale works to expand the outer enclosures and to strengthen mountain and lowland sectors; successive major campaigns of fortress construction culminated in the late 1580s.

In 1590 Toyotomi Hideyoshi besieged Odawara with a vast force, deployed overwhelming supplies and simultaneously neutralised Hojo garrisons across the region; after a three-month operation the Hojo surrendered. Following the campaign Tokugawa Ieyasu received the former Hojo domains and placed his trusted retainer, the Okubo family, at Odawara. The first Okubo lord was assigned 40,000 koku around the castle and an additional 5,000 koku from Toyotomi sources, creating Odawara Domain. The Tokugawa and their vassals altered, repaired and in several phases demolished parts of the outer works; the castle passed through direct shogunal control and then returned to daimyo rule under several families during the Edo period.

Two major earthquakes in the Edo era—1633 and 1703—caused severe damage; the tenshu collapsed in 1703 and was rebuilt in 1706. Most castle buildings were removed in the early Meiji years (1870–1872); the site later hosted an imperial villa (1901) that was destroyed in the 1923 Great Kanto Earthquake. The 20th century saw piecemeal reconstruction: a reduced-scale turret in 1935, post-quake stonework repairs in 1930–31, and the post-war program that produced the present tenshu and the park.

Archaeology, protection and surviving medieval traces

Archaeological work has produced several discoveries: remains of moats and a Hojo-period pond and garden were found in 2013 in the former rice-storehouse enclosure; earthwork and moat traces have been confirmed at multiple points across the outer ring and on the Hachiman-yama ridge. The site was designated a national Historic Site on 8 August 1938; additional areas were added in 1959 and again on 4 May 1977, with further additions in later years. The protected zone now spans multiple Odawara neighbourhoods and includes both flatland and mountain segments of the former total enclosure.

Notable medieval remains listed in surveys include the Komine great trench, surviving earthen banks and middle moats, parts of the Hachiman-yama enclosures, the new third-outer-earthen bank, the Inari-mori moat, pocket-park mounds beside a local high school that preserve shoji-bori traces, remaining banks near the Okubo Shrine, the dry trench and banks around the O-kane-no-dai high point, double banks near the Hayakawa entrance, and embankments at the Koda and Rengejoin approaches. These fragments make Odawara an unusually complete example of adjacent medieval and early-modern defensive systems.

FAQ

Where is Odawara Castle located?

Jonai 6-1, Odawara City, Kanagawa Prefecture.

Which clan used Odawara Castle as its principal seat?

The later Hojo clan used Odawara Castle as its headquarters for five generations.

What is the castle’s total enclosure (sogamae)?

A continuous system of earthen banks and dry moats running roughly 9 kilometres around the town and castle.

When was the site first designated a National Historic Site?

8 August 1938.