The Siege of Osaka comprised two campaigns, the Osaka Winter Campaign (1614) and the Osaka Summer Campaign (1615), in which the Tokugawa shogunate eliminated the Toyotomi clan, and thus the last major threat to Tokugawa hegemony, setting the stage for 250 years of near-total domestic peace.
Following the battle of Sekigahara in 1600, the Toyotomi, under Toyotomi Hideyoshi's heir Toyotomi Hideyori, remained in Osaka and maintained a strong, if temporarily quieted, body of supporters. Tokugawa Ieyasu based himself in Osaka castle for the first few years of the 17th century, but by the 1610s, Toyotomi Hideyori (17 years old in 1610) was regaining strength. He worked to have his father's temple of Hôkô-ji rebuilt, and in 1614 requested shogunal permission to have the temple rededicated; a series of communications back and forth between the Toyotomi and Tokugawa culminated in one which the Tokugawa interpreted as containing a hidden message challenging Tokugawa hegemony. On 1614/9/7, in anticipation of conflict with the Toyotomi, the Tokugawa ordered the heads of the Môri, Nabeshima, Shimazu, and several other clans to come to Edo to formally re-affirm their oaths of loyalty to Ieyasu and his son, the Shogun Hidetada, in person.
Ieyasu and Hidetada issued orders on 10/1 for a number of daimyô of eastern Japan to muster forces in preparation for an attack on Osaka. A number of daimyô previously loyal to the Toyotomi, who were already resident in Edo at that time became, essentially, political hostages, while a number of more trusted lords were made to travel to Sunpu, where they were interviewed by Ieyasu to confirm their loyalty.
Ieyasu and Hidetada journeyed separately to Kyoto, with a combined force of perhaps as many as 200,000 men. The Toyotomi-loyal armies, based in Osaka castle, one of the most impressive fortifications in the realm, are said to have perhaps numbered as many as 100,000. The Tokugawa forces began setting themselves up in hills surrounding Osaka on 11/15, and on 11/19 began their assault on smaller Toyotomi-loyal fortresses with the battle of Kizugawa.
The assault on Osaka castle itself began on 12/16. Ieyasu employed a number of heavy cannon (some of European manufacture, and some made in Sakai), but failed to do any significant damage to the keep. The noise, however, is said to have had a noteworthy effect on the defenders, an "assault on [their] minds" which made it difficult to relax or sleep. Though the Tokugawa forces made little actual progress, in terms of damaging the castle or gaining territory, this initial conflict ended in a limited ceasefire. Throughout the bombardment, Tokugawa and Toyotomi representatives exchanged negotiations as to a set of demands both sides could agree to; eventually, Hideyori agreed to a set of conditions that included guaranteeing his enfeoffment & income on a fief equivalent to Osaka, guaranteeing his own personal safety, and guaranteeing that his mother, Yodo-dono, would not be made hostage in Edo. The two sides agreed to a ceasefire, and Ieyasu returned to Kyoto, though Hidetada remained at Osaka, and oversaw the filling in of the moat. Most mythologizing accounts written long after the fact exaggerate the ways the Tokugawa used subterfuge to somehow convince the Toyotomi to allow this, but in truth the extent to which the inhabitants of the castle agreed to this, or even knew about this Tokugawa intention, is unclear.
The Tokugawa forces largely finished filling in the moats of the Ninomaru and Sannomaru by the end of the first month of 1615. Hidetada departed Osaka for Kyoto on 1/19, and Kyoto for Edo on 1/28; a messenger reported to Ieyasu on 2/1 that this work had been completed. After much planning, Ieyasu departed Sunpu for Osaka on 4/4, followed by Hidetada, who departed Edo on 4/10. Ieyasu took up temporary residence at Nijô castle beginning on 4/18, and Hidetada at Fushimi castle on 4/21, welcoming numerous lords (and their considerable armies) over the next several weeks.
The Summer Campaign began in earnest on 5/5, with Tokugawa forces reaching Osaka proper on 5/7. Rather than face another siege, Hideyori led his 50,000 or so men to meet the Tokugawa forces - some 150,000 in total - in battle at Shitennô-ji, a short distance south of the castle. The Toyotomi forces were crushed in this battle of Tennô-ji, and Osaka castle came under attack once again, with a fire blossoming from inside the castle (from the kitchens, according to some sources), and a number of the Toyotomi generals anticipating defeat and committing suicide. Countless commoner residents of Osaka, and castle staff, were killed as they attempted to flee the violence enveloping their city.
In contrast to the month-long siege of the previous winter, this second assault was successful after more or less only a single day of fighting. By the end of the day on 5/7, the castle had effectively fallen. The following day, Hideyori and his mother Yodo-dono are believed to have killed themselves (the precise circumstances remain unclear), while Hideyori's wife Senhime (a granddaughter of Tokugawa Ieyasu) was sent out, alive, to be taken in by the Tokugawa forces.
Following the fall of the castle, and of the Toyotomi clan, Tokugawa Ieyasu made efforts to recover artifacts and heirlooms owned by the Toyotomi, including ceramics, swords, tea instruments and a variety of other objects. Some of these objects were repaired (ceramics, with lacquer), or, in the case of swords, reforged. Historian Morgan Pitelka identifies this as not only a result of Ieyasu's love of art and history, but also a profoundly political act, seizing ownership of these treasures previously owned by the Toyotomi.
- Morgan Pitelka. "Art, Agency, and Networks in the Career of Tokugawa Ieyasu." in A Companion to Asian Art and Architecture. Wiley-Blackwell, 2011, 460-461.
- Morgan Pitelka, Spectacular Accumulation, University of Hawaii Press (2016), 128-135.
- Pitelka, Spectacular Accumulation, 132.