Location and History
Battlefield of Crucial Event
The Battle of Sekigahara have been one of the most crucial events in the Japanese History. The East squad led by Ieyasu Tokugawa and the West squad led by Mitsunari Ishida battled each other at Sekigahara Field in 1600 before the Tokugawa Shogunate was established. Most Japanese people know about Skigahara, but what about Ogaki Castle? In fact, the castle might have become the battle field of the crucial event if the situation changed (if Mitsunari decided to stay in that castle).
Ogaki Castle as Important Point
Ogaki Castle was located in the western part of Mino Province (now Gifu Prefecture) connecting to western Japan trough Sekigahara. It is uncertain when the castle was first built, but it became important as the country had been unified in the late 16th Century during the Sengoku Period. The ruler, Hideyoshi Toyotomi said “Ogaki Castle is an important point” and actually sent his relatives to the castle as its lords. The castle was built on a plain land, but surrounded by several moats and rivers, which looked like a Water Castle.
After Hideyoshi died in 1598, a political conflict began between Ieyasu Tokugawa and Mitsunari Ishida. Mitsunari doubted Ieyasu would take over the power of Hideyoshi’s young son, Hideyori who was still the ruler of Japan. Ieyasu went to eastern Japan to conquer the Uesugi Clan who were against Ieyasu in June 1600. Mitsunari raised an army to defeat Ieyasu in July in western Japan. The East and West squads were expected to fight in central Japan including Ogaki Castle and Sekigahara. Mitsunari stayed in Ogaki Castle as his stronghold and built several battle castles, such as Nangusan Castle, on the mountains behind Ogaki Castle for his allies to stay. He was waiting for Ieyasu’s attack at the castle doing as best as he could. He also built large mountain castles such as Matsuoyama Castle around Sekigahara Field to call for a great warlord, Terumoto Mori and his master, Hideyori to support him. If his plans came true, Ieyasu might have been defeated because Hideyori was still Ieyasu’s master as well.
Why did Mitsunari leave Castle?
However, on September 15th, Mitsunari suddenly got away from the castle, fought against Ieyasu at Sekigahara Field, and defeated in a day. Why did Mitsunari cancel his own plan and choose the field battle he probably dislike but Ieyasu was more familiar with? The long-accepted theory says Mitsunari noticed Ieyasu tried to skip Ogaki Castle and attack western Japan directly. Mitsunari and his allies were one jump ahead of Ieyasu, and took up their positions at the field. They fought well in the first part, but finally got defeated by the betrayal of Hideaki Kobayakawa, one of their allies, during the battle. This story is dramatic, so Japanese people believed it for a long time. However, it was first seen in war chronicles in the Edo Period, about 60 years later than the actual battle. I also think the reason above is too weak for Mitsunari to leave the castle.
Some new studies may tell us the real reasons why Mitsuhide left Ogaki Castle. According to these studies, Hideaki Kobayakawa was expected to support the East quad earlier than what the previous theory says. Hideaki occupied Matsuoyama Castle and moved to Sekigahara Field before the battle against Mitsunari’s plan. If he stayed, he could have been attacked on both sides. Mitsunari might have noticed Hideaki’s movement, so this may be why he quickly moved to Sekigahara to avoid the worst situation. One theory says Mitsunari tried to get to another mountain castle, called Tama Castle, to fight against Ieyasu and Hideaki, but was unfortunately defeated around Sekigahara Field. After the battle, some Mitunari’s retainers still stayed in Ogaki Castle, however, they were outnumbered. They surrendered after being besieged by the East squad for about a week.
Ogaki as City of Water
After the Battle of Sekigahara, Ogaki Castle was still recognized as an important point connecting eastern and western Japan. Several different lords governed and improved the castle. For example, the Ishikawa Clan completed the Outer Moat and the Matsudaira Clan renovated the four-level Main Tower. The tower was in the Main Enclosure which is connected with the Second Enclosure where the Main Hall for the lord was. Both enclosures were surrounded by the Inner Moat. Overall, the tripled moats surrounded the castle. In addition, the castle town was consolidated with the castle by waterways and rivers. That’s why Ogaki City has been called The city of water. Since 1635, the Toda Clan governed the castle and the area was called the Ogaki Domain until the end of the Edo Period.
