Toyotomi Hideyoshi was a great unifier in Japan. He was a general under Oda Nobunaga and took power after his death. He controlled most of Japan and reduced most of the daimyo’s power. In 1583, he started building Osaka Castle on the previous site of the Ishiyama Hongan-ji Temple, which was destoryed by Oda Nobunaga. It was built to symbolize Toyotomi Hideyoshi's power and military strength. Osaka Castle was also built to be the biggest castle in Japan, surpassing Oda Nobunaga’s Azuchi Castle. Later on, Himeji Castle became the biggest castle in Japan. 

The construction of Osaka Castle started with Toyotomi Hideyoshi in 1583 as a sign of power and military strength. The keep was finished two years later, and the full castle was finished in 1597. The castle was “[b]uilt on the great slope (o-saka)” (Turnball 143).  The castle was built around rivers and reed beds. The walls of the castle got higher as a person got closer to the keep and were built in a ring. The keep was 5 stories tall but had 8 internal floors. As Toyotomi Hideyshi loved gold, the exterior was decorated with many gold leaves and ornaments. The castle had strong defensive structures, with some walls being built 20 meters high. The walls were built using a technique called burdock piling. The stones on the walls had engravings of family crests of daimyo’s that contributed to the construction. The keep was burned down in the siege of Osaka during the summer campaign and “[i]n 1655, the main tower was struck by lightning and burned down” (Japan Experience). The keep was not rebuilt until 1931, when modern techniques were used to rebuild it.  

After the death of Toyotomi Hideyoshi, Toyotomi Hideyori took control of Osaka Castle. During this time, the power of the Toyotomi clan decreased due to a rise in power in the Tokugawa clan. The Tokugawa clan was led by Tokugawa Ieyasu, and tensions rose between the clans. This resulted in the siege of Osaka in 1614-1615. The siege was split up into two seasons, the summer and winter campaigns. During the winter campaign, Osaka Castle held up against the attacks, but in the summer campaign, it was burned down by the Tokugawas. This caused Hideyori and his mother to commit suicide as the Castle was falling. Tokugawa Ieyasu ordered the reconstruction of Osaka Castle in 1620. When the Tokugawa clan rebuilt the castle, they built the castles higher and the moats deeper. The keep was rebuilt with 5 stories, taller than Hideyoshis, and it was rebuilt internally as well. The castle became a sign of superiority for the Tokugawa clan over the Toyotomis. Osaka Castle became an important place for the Tokugawa clan by controlling the area and housing many samurai. 

Osaka Castle was built on two raised platforms that were supported by stone walls built from a method called burdock piling. The keep, which was the main part of the castle, was built from white plastered walls, wood, and golden leaves. On the top ridge, there is a golden sachi, which was a mythical tiger fish. The main entrance was through the Ote-mon gate, and there were many yagura’s or turrets on the walls. Many baileys or marus that formed a concentric circle and storehouses surrounded the keep. The castle also has Nishinomaru Garden which provided a view point of the castle and the cherry blossoms.