Odaka Castle Ruins / Marugane Fort Ruins / Washizu Fort

A Battlefield at the Edge of Nagoya

Before dawn on a spring morning in 1560, two small hilltop forts above the village of Ōdaka were stormed and burned. A few hours later, a short distance to the east, the warlord Imagawa Yoshimoto was killed in a sudden rainstorm by a far smaller force led by Oda Nobunaga. The clash, known as the Battle of Okehazama, is one of the most studied upsets in Japanese history, and the quiet ridges now folded into the southern edge of Nagoya were where its opening moves played out.

The site has a slightly awkward but precise official name: Ōdaka Castle Site, with the appended Marune Fort Site and Washizu Fort Site. The three locations were designated together as a single National Historic Site in 1938. They sit on the low hills at the northern tip of the Chita Peninsula, a position that mattered enormously when the shoreline of Ise Bay still pushed much closer inland than it does today.

Ōdaka Castle itself was a modest fortification, roughly 106 meters east to west and 32 meters north to south, ringed by a double moat. It was built in the early sixteenth century by a local lord, Hanai Bitchū-no-kami, and later passed to the Mizuno family. By the late 1550s it had fallen under the control of the Imagawa, a powerful clan based in Suruga Province to the east, and it became a forward outpost in their long contest with the Oda over the border province of Owari.

Why Three Sites Were Listed as One

To understand why a castle and two forts share a single designation, it helps to picture the standoff that bound them together. Ōdaka was an Imagawa island inside Oda territory. To choke it off, Oda Nobunaga ringed the castle with a series of siege forts, severing the supply lines that linked Ōdaka to the larger Imagawa stronghold at Narumi Castle nearby. Marune Fort sat to the east, Washizu Fort to the northeast, with other small forts closing the western and southern approaches.

The castle and its besieging forts are therefore two halves of one military situation, which is why the Agency for Cultural Affairs lists Marune and Washizu as "appended" components of the Ōdaka designation rather than as separate properties. The official criterion for the listing places it among castle sites and battle sites significant to political history. What earns it that status is not architecture, since almost none survives, but the role these earthworks played on a single decisive day.

That day was the nineteenth of the fifth month of 1560. On the night before, a nineteen-year-old vassal serving in the Imagawa army slipped a convoy of rice into the encircled Ōdaka Castle, threading the gaps in the Oda cordon. His name at the time was Matsudaira Motoyasu. Two decades later, as Tokugawa Ieyasu, he would unify Japan and found a dynasty of shoguns that governed the country for more than 250 years. The "Ōdaka provisioning," as the feat is remembered, was an early test of the man who would become the most consequential figure of the age.

At first light the next morning, the Imagawa turned on the siege forts. Marune and Washizu were both taken in hours of hard fighting; the commander defending Marune, Sakuma Morishige, was killed there. By tradition the assaults are credited to different Imagawa captains, and old and modern accounts disagree on exactly who led which attack, but the outcome is not in doubt. The forts fell, the Imagawa thought the road into Owari lay open, and within hours Yoshimoto himself was dead and the campaign reversed. Ōdaka lost its purpose almost immediately and was abandoned not long after.

What You Actually See Today

Visitors expecting stone walls and a tower will not find them. What survives is the shape of the land: the cut of dry moats, the raised platforms of the inner and second baileys, and an earthen causeway across what was once water. Reading these requires a little imagination, and the reward is in the reading.

Start at Ōdaka Castle Park, which occupies the old castle precinct. A stone marker carved with the words for "Ōdaka Castle Site" stands on the main bailey, and a small Hachiman shrine sits just to its west. From the second bailey you can look across to the main one and trace how the ground steps up and falls away. Some of the flat lawn underfoot was moat in the castle's working life. Nagoya's education board has even run ground-penetrating radar surveys here since 2019 to map the buried structure more precisely.

The two forts are short walks away and sit on wooded knolls that rise above the surrounding houses. Washizu Fort, now a small park, carries a stone monument marking its position; Marune Fort, roughly 800 meters to the south, is topped by a memorial to those who died defending it. A practical tip from people who have made the circuit: visit the castle first and look toward the forts before climbing them, because the trees on the summits block the long views, and the spatial logic of the siege is far easier to grasp from below than from the top of a thicket.

Getting There and Nearby

The most straightforward approach is by train. From JR Ōdaka Station on the Tōkaidō Main Line, the castle park is about a twelve to fifteen minute walk, and signs mounted on utility poles guide you through the residential lanes. All three sites can be linked on foot in a half-day loop, which is the way most history-minded visitors tackle them.

Driving is harder than it sounds. There is no parking at the castle, and the streets immediately around it are tight enough that locals advise against bringing a car close. Many people instead park at the large Ōdaka Ryokuchi green space a little further off and walk in. The area is residential, with few cafés or shops right by the sites, so it pays to bring water, especially in summer, when the wooded fort hills also attract mosquitoes.

If you want to round out the day, Ōdaka Ryokuchi is a sprawling park with woodland trails and family attractions, and the wider Okehazama battlefield area to the east has its own monuments and small museums devoted to the 1560 clash. Together they make Ōdaka a natural first stop on a longer walk through the events of that morning.