Kiyomasa Kato (1562-1615) was a Toyotomi and Eastern Army general who was one of the "Seven Spears of Shizugatake". He was perhaps best known not for a feat in battle in Japan, but in the invasion of Korea in 1592~1598, leading the capture of Hanseong (Seoul), the capital of Choson. He died in the Osaka Campaign, fighting to save the Toyotomi household.
Kiyomasa Kato was born in Aichi, Owari Province, to Kiyotada Kato and another peasant. He enlisted in the army in 1582 as a regular footsoldier in the Hashiba Army, led by Hideyoshi Hashiba. He gained Hideyoshi's attention in the Battle of Yamazaki that year, as his skills stood out.
Kiyomasa became considered one of Hideyoshi's "children", alongside Masanori Fukushima and Mitsunari Ishida, two other young retainers who also stood out in battle. Kiyomasa, along with Masanori, became one of the "Seven Spears of Shizugatake" after the 1583 Battle of Shizugatake, and became rapidly promoted to General. A year later, he proved himself a greater warrior fighting alongside Sakon Shima at the Battle of Komaki-Nagakute against the Tokugawa. Kiyomasa was granted a reward for his services: command of the invasion force that would land in Kyushu to support the Tachibana against the Shimazu, led by Yoshihiro Shimazu. Kiyomasa fought well, and victory was his.
Kiyomasa Kato later took part in the Siege of Oshi Castle in 1590, where Hideyoshi Hashiba's massive army of warriors from all across the land gathered to stomp down upon the Hojo clan, the last clan that had not yet submitted to the Toyotomi. Kiyomasa fought alongside Mitsunari, and began to grow a dislike for him, as he was arrogant and selfish.
Kiyomasa Kato took part in the First Invasion of Korea in 1591-1593, capturing Hanseong in 1592. He took part in the second invasion of 1597-1598, but with less distinguishment. When Hideyoshi died in 1598, a succession dispute broke out. Kiyomasa became allies with Masanori Fukushima, who had formed an Anti-Ishida Coalition of former Toyotomi vassals, hoping to take Mitsunari's head if it meant that he would become Shogun.
However, their assassination attempt in Kyoto failed, and the coalition forces were defeated by Ieyasu Tokugawa and Kanetsugu Naoe, who had come to aid him. The next round of the succession crisis saw the Tokugawa and Toyotomi stand off. Mitsunari formed the Western Army, while Ieyasu formed the Eastern Army. Although Kiyomasa was committed to protecting the Toyotomi household in return for Hideyoshi's kindness, the Tokugawa had better military and political power, and the Western Army was short of morale and manpower, and, needless to say, unity.
Kiyomasa sided with the Tokugawa, thinking that they would let the Toyotomi live after they crushed Mitsunari Ishida's rebellion. Kiyomasa served with distinction at the Battle of the Ishigaki Plains in Kyushu, where he assisted Kanbei Kuroda in defeating the Tachibana, Otomo, and Shimazu, who sided with the Western Army. He returned to Shinano Province in enough time to fight in the Battle of Sekigahara against Mitsunari himself, and struck down several enemy warriors in battle. Kiyomasa was wounded in the fighting, but lived through the battle and recovered quickly.
After the defeat of the Western Army, Kiyomasa urged Ieyasu Tokugawa to arrange a meeting between the Tokugawa and Toyotomi at Naito Castle, but it was futile; Kanbei Kuroda decided that the Toyotomi were a dried out husk, and if ignited, the land would return to chaos. In other words, he decided that they must be crushed. Kiyomasa returned to the Toyotomi resistance movement, and fought at Osaka Castle against the Tokugawa.
The Tokugawa clan eventually overwhelmed the garrison, and Kiyomasa was slain in battle. He was noted for being a great warrior during his lifetime, and a loyal one.