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.

The Tokugawa forces were repeatedly repelled, and Sanada's troops launched a number of counterattacks, even breaking through the siege lines.

[1] By December 18, all the outlying forts and waterways had fallen but the Sanada Maru proved impregnable.

[4] Sanada Maru has appeared in part or in full for different media including stage, screen and radio.