The Winter Siege of Osaka began on November 19, 1614 and lasted until January 22, 1615, when Ieyasu led three thousand men across the Kizu River, destroying the fort there. A week later, he attacked the village of Imafuku with 1,500 men against a defending force of 600. With the aid of a squad of arquebusiers, the Tokugawa claimed victory once again. Several more small forts and villages were attacked before the siege on Osaka Castle itself began on December 4, 1614.

Sanada Yukimura built a small fortress called Sanada-maru in the southwest corner of Osaka Castle. The Sanada-maru was an earthwork barbican defended by 7,000 men under Yukimura's command. From there, he defeated the Tokugawa forces (approximately 30,000 men) with groups of 6000 arquebusiers. The Shogun's forces were repeatedly repelled, and the Sanada troops launched a number of attacks against the siege lines, breaking through three times. Ieyasu then resorted to artillery, which included 17 imported European cannons and domestic wrought iron cannons, as well as sappers employed to dig under the walls of the fortress. The fortress was impregnable; the Tokugawa suffered many losses.

Ieyasu gave up trying to destroy the castle during this battle, and sued for peace with Toyotomi Hideyori. He proposed a condition for the reconciliation, i.e. to destroy the outer moat of the castle. When his envoy entered the castle grounds, they destroyed not only the outer moat but the inner moat as well.