Sanada Maru

Sanada Maru 真田丸
southeast corner Osaka Castle, Japan
"Syokoku kojō no zu - Sanada Maru", map of the Sanada Maru. Collection of the Hiroshima City Central Library.
Coordinates	34°40′23″N 135°31′44″E / 34.673026°N 135.528767°E / 34.673026; 135.528767
Site information
Condition	destroyed
Site history
Built by	Sanada Yukimura
Events	Siege of Osaka

The Sanada Maru (真田丸 （さなだまる）, Sanada Maru) was a small fortification attached to Osaka castle. It is famous for being impregnable and playing a key role in defending the castle in the winter of 1615. Later, it was forcefully destroyed despite being exempt from the reconciliation condition.

Osaka castle was built on the Uemachi plateau enclosed by the Yodo River and the Yamato River. It was well fortified to the north but weakly guarded to the southern Tennōji plateau. Sanada Yukimura build the fortification in front of the outer moat, at the Kuruwa port, at the southeastern Hirano-guchi (平野口) gate and beside the Kuromon-guchi (黒門口) gate. Due to its position, Sanada Maru became an obstacle to the main Tokugawa force during the Siege of Osaka.

By 1615, after its destruction, the tower keep era had reached its peak and construction declined with the establishment of the Pax Tokugawa, which lasted until the Meiji period in the late 19th century.

In 1614, Osaka castle, the stronghold of the Toyotomi clan represented the last obstacle to Japan's unification under the Tokugawa hegemony. Toyotomi Hideyori appointed Sanada Yukimura as the garrison commander due to his experience opposing Ieyasu's army in his castle at Ueda during the Sekigahara campaign. At that time the castle had two moats, which still exist, and Hideyori's engineers created an outer moat by cutting a channel between the canal that existed to the west and the Nekoma stream which flowed from south to north on the eastern side.