Edo Castle, also known as Chiyoda Castle, is a flatland castle that was built in 1457 by Ota Doukan. It is located in Chiyoda in Tokyo, then known as Edo, Toshima District, Musashi Province. Tokugawa Ieyasu established the Tokugawa shogunate here. It was the residence of the shogun and location of the shogunate, and also functioned as the military capital during the Edo period of Japanese history. After the vacation of the shogun and the Meiji Restoration, it became the Tokyo Imperial Palace. Some moats, walls and ramparts of the castle survive to this day. However, the grounds were much more extensive during the Edo period, with Tokyo Station and the Marunouchi section of the city lying within the outermost moat. It also encompassed Kitanomaru Park, the Nippon Budokan Hall and other landmarks of the surrounding area.
The warrior Edo Shigetsugu built his residence in what is now the Honmaru and Ninomaru part of Edo Castle, around the end of the Heian or the beginning of the Kamakura period. The Edo clan perished in the fifteenth century as a result of uprisings in the Kanto region, and Ota Dokan, a retainer of the Ogigayatsu Uesugi family, built Edo Castle in 1457.
The castle later came under the control of the Late Hojo clan. The castle was vacated in 1590 due to the Siege of Odawara. Tokugawa Ieyasu made Edo Castle his base after he was offered six eastern provinces by Toyotomi Hideyoshi. He later defeated Toyotomi Hideyori, son of Hideyoshi, at the Battle of Sekigahara in 1600, and emerged as the political leader of Japan. Tokugawa Ieyasu received the title of Seii Taishōgun in 1603, Edo became the center of Tokugawa administration.
Initially, the area was not habitable with parts of it lying under water. The sea reached the later Nishinomaru area of Edo Castle, and Hibiya was a beach. The land was changed for the construction of the castle. Most construction took place starting in 1593 and reached completion in 1636 under the grandson Tokugawa Iemitsu. By this time, Edo had a population of 150,000.
The grounds grew with the addition of Nishinomaru, Nishinomaru-shita, Fukiage, and Kitanomaru areas to the existing Honmaru, Ninomaru, and Sannomaru areas. The perimeter measured 16 km.
The daimyo were required by the shogun to supply building materials or finances, a method used by the shogunate to keep the powers of the daimyo in check. Large granite stones were moved from afar, the size and number of the stones depending on the wealth of the daimyo. The wealthier ones had to contribute more. Those who did not supply stones were required to contribute labour in tasks like digging the large moats and flattening hills. The earth that was taken out from the moats were used as landfill for sea-reclamation or to level the ground. Thus the construction of Edo Castle laid the foundation for parts of the city where merchants were able to settle.
At least 10,000 men were involved in the first phase of the construction and more than 300,000 in the middle phase. When construction ended, the castle had 38 gates. The ramparts were almost 20 metres and the outer walls 12 metres high. Moats in rough concentric circles were dug throughout for further protection. Some of the moats reached as far as Ichigaya and Yotsuya areas, parts of the ramparts survive to this day. Either the sea or the Kanda river surrounded it, enabling navigation by ships.
Various fires over the centuries damaged or destroyed parts of the castle, since Edo and the majority of the buildings were constructed out of wood.
On April 21, 1701, in the Great Pine Corridor (Matsu no Rouka) of Edo Castle, Asano Takumi-no-kami drew his short sword and attempted to kill Kira Kozuke-no-suke for insulting him. This triggered the events involving the Forty-seven Ronin.