Great Unifiers of Japan: Oda Nobunaga, Toyotomi Hideyoshi, Tokugawa Ieyasu
Throughout the 15th and 16th centuries, Japan was in a constant state of civil war as a result of a weakened Ashikaga shogunate. This period of time in Japan’s history is referred to as the Sengoku period, also known as the Warring States period. Three men would be responsible for reunifying the nation of Japan: Oda Nobunaga, Toyotomi Hideyoshi, and Tokugawa Ieyasu, who would eventually be recognized as the three “Great Unifiers.”
In 1534, Oda Nobunaga was born as the heir of the powerful Oda clan, which presided over Owari Province. However, in 1551, his father died unexpectedly, causing a succession crisis as some in the Oda clan opposed Nobunaga. By the end of the decade, Nobunaga would consolidate his leadership over the clan by eliminating his enemies. After establishing his authority, he sought to defend his territory against the rival Imagawa clan, which launched an invasion of Owari Province in 1560 with roughly 25,000 men. Although Nobunaga could only muster around 2,000–3,000 soldiers in response, he was able to pull off an impressive win at the Battle of Okehazama, decimating the leadership of the Imagawa clan through a surprise attack. This victory earned him the loyalty of many samurai and minor warlords who controlled various territories, such as the Matsudaira clan. Over the next few years, his power would continue to grow as he conquered the Mino, Ise, and Omi Provinces, culminating in a march to the capital city of Kyoto where he helped to install a new shogun, Ashikaga Yoshiaki, to lead the Ashikaga shogunate.
However, Yoshiaki would secretly conspire with other daimyo (warlords) to get rid of Nobunaga. This anti-Nobunaga alliance would spring into action in 1570, but Nobunaga would destroy each enemy that opposed him, such as the Azai, Asakura, Ikko-ikki, Mori, and Takeda clans. Eventually, he drove Yoshiaki out of Kyoto into exile, effectively ending the Ashikaga shogunate. Nobunaga’s ultimate triumph at the Battle of Nagashino over his adversaries paved the way for his rule of Japan. By 1580, he was the most powerful warlord as he ruled over 20 provinces, essentially becoming the de facto leader of the country. On the verge of unifying the country, he decided to relax at the Honno-ji temple in Kyoto. Unfortunately, one of his trusted generals, Akechi Mitsuhide, betrayed and killed both Nobunaga and his heir in 1582. This series of events would allow Toyotomi Hideyoshi, another one of Nobunaga’s most trusted retainers and distinguished generals, to finish what Nobunaga started.
In 1537, Toyotomi Hideyoshi, who was initially known as Kinoshita Tokichiro, was born into a peasant family. He would later become an infantryman for the Oda clan, rising through the ranks and earning Nobunaga’s trust due to his efforts in the Battle of Okehazama. Over the years, he continued to aid Nobunaga in his quest to conquer Japan, eventually becoming one of his most trusted generals and taking the name Hashiba Hideyoshi. When Hideyoshi discovered Mitsuhide’s betrayal, he would avenge his lord’s death at the Battle of Yamazaki by defeating and slaying Mitsuhide. As Nobunaga’s heir was yet to be determined, infighting began amongst his generals; these tensions resulted in the Battle of Shizugatake, where Hideyoshi defeated his rivals and consolidated his position as Nobunaga’s successor. Now the strongest warlord in Japan, he established the Toyotomi clan in 1585 and changed his name to the one that most know him by: Toyotomi Hideyoshi. Hideyoshi went on to destroy any remaining resistance to his total rule of Japan, as his forces would cut down the warrior monks of Negoro-ji, conquer the islands of Shikoku and Kyushu, and crush rebellious groups such as the Hojo clan. The final battle of Hideyoshi’s campaign would involve the suppression of the Kunohe rebellion; with this last victory, he was able to complete the unification of Japan in 1591.
Although one might think that Hideyoshi would be satisfied with his accomplishments, he yearned for more glory and sought to conquer Ming China. He would ask for safe passage into China through Korean soil and be refused, thus resulting in him ordering a full-scale invasion of Korea. While his ground troops were initially very successful as they captured the capital of Korea within months, his navy was destroyed by legendary Korean Admiral Yi Sun-shin, prolonging an increasingly costly war for Hideyoshi. After multiple years of waging war in Korea, he suddenly died in 1598, forcing the withdrawal of all Japanese soldiers back to their home islands. As a result of his failure to capture Korea, his son Toyotomi Hideyori inherited a weakened position of power due to the financial losses and reduced manpower caused by the war. This would allow another ambitious warlord, one by the name of Tokugawa Ieyasu, to wrestle control of Japan from the Toyotomi clan.
In 1543, Tokugawa Ieyasu, who was initially known as Matsudaira Takechiyo, was born as the heir of the Matsudaira clan, which was an enemy of the Oda clan at the time. He was initially abducted by the Oda clan at around the age of five, but was later rescued by their rivals, the Imagawa clan. As he grew older, he eventually changed his name to Matsudaira Kurandonosuke Motoyasu. After Oda Nobunaga became the leader of the Oda clan and won the Battle of Okehazama over the Imagawa clan, Motoyasu decided to ally with him. Changing his name again to Matsudaira Ieyasu, he strengthened his clan’s control over the Mikawa Province by destroying rebellious groups within the region. Then, in 1567, he would start the family name “Tokugawa” and finally settle on the name etched into Japanese history: Tokugawa Ieyasu.
Ieyasu, like Hideyoshi, also assisted Nobunaga in his battles; he was especially helpful in defeating the Takeda clan and winning the Battle of Nagashino. When Nobunaga was assassinated, however, Ieyasu would not participate in the following battles of Yamazaki and Shizugatake as he chose to prioritize caution. A year later, Ieyasu would engage in a conflict with Hideyoshi over the heir to Nobunaga, which would prove to be fruitless for both sides. After both men made peace, Ieyasu would become an ally in Hideyoshi’s quest to conquer the rest of Japan, aiding in victories over the Hojo clan and the Kunohe rebellion. Interestingly, when Hideyoshi began his war in Korea, Ieyasu cautiously and intelligently kept his forces in Japan. While Toyotomi power was weakened by the failed invasion, Tokugawa soldiers did not participate in the campaign and thus saved their strength. Upon Hideyoshi’s death, a power vacuum emerged, presenting an opportunity that Ieyasu would take advantage of.
After Hideyoshi’s death, plans were made on all sides for a war to determine his successor. Control of Japan would be determined between Ishida Mitsunari (one of Hideyoshi’s loyal bureaucrats), who commanded the Western Army made up of many clans from Western Japan, and Tokugawa Ieyasu, who commanded the Eastern Army made up of many clans from Eastern Japan. A few battles between these forces would eventually culminate in the largest and most important conflict of Japanese feudal history: the Battle of Sekigahara. While the Eastern Army had only 75,000 men to the Western Army’s 120,000, many Western Army soldiers and commanders decided to defect to the Tokugawa side during the battle. As a result of these defections, the Western Army’s right flank collapsed, causing a full retreat and subsequent disintegration of Ishida’s forces. Many Western Army leaders, including Ishida himself, were executed, which would allow Ieyasu to control Japan as the shogun. This marked the end of the Sengoku/Warring States period and the beginning of the Tokugawa shogunate, which would finally bring a period of peace and stability to a unified Japan for the next 260 years (1603 to 1868).
Oda Nobunaga started, Toyotomi Hideyoshi completed, and Tokugawa Ieyasu consolidated. Japan would see a new era: the Tokugawa period (also referred to as the Edo period), known especially for its class system and isolationist policies of Sakoku. While the Tokugawa shogunate would eventually be overthrown during the Meiji Restoration, giving rise to the Empire of Japan, the legacy that these three great men left behind continues today in the modern unified country of Japan.
Written by Brian Kim, Edited by Koushik Chennakesavan
