First Siege of Sogō Castle
Date: 8/11 to winter season of Tenshō 10 (1582)
Location: The environs of Sogō Castle in the Yamada District of Sanuki Province
Synopsis: Chōsokabe Motochika, the sengoku daimyō of Tosa Province, invaded Sanuki Province and, together with his son, Kagawa Chikakazu (who had earlier been adopted by the Kagawa clan of Sanuki) laid siege to Sogō Castle defended by Sogō Masayuki and a small garrison. Owing to the support of Maeda Munekiyo who disrupted the besieging army with ninja tactics, and with the onset of the winter season, the Chōsokabe and Kagawa forces finally withdrew without taking the castle.
Lord: Chōsokabe Motochika
Commanders: Kagawa Chikakazu, Kagawa Yukikage, Kōzai Yoshikiyo
Forces: Army of Kagawa Chikakazu: 10,000; army of Chōsokabe Motochika: approximately 2,500; army of Kōzai Yoshikiyo: approximately 1,000
The First Siege of Sogō Castle occurred from 8/11 to the winter period of Tenshō 10 (1582) in the environs of Sogō Castle in the Yamada District of Sanuki Province.
In 1578, Chōsokabe Motochika, the sengoku daimyō of Tosa, invaded Sanuki. In 1581, a settlement was made whereby Kagawa Yukikage, the deputy military governor of four districts in western Sanuki, agreed as a condition of peace to accept Chikakazu (the second son of Motochika) as his adopted son. Chikakazu then inherited the surname of Kagawa.
On 8/6 of Tenshō 10 (1582), the combined forces of the Chōsokabe and the Kagawa clans attacked Fujio Castle where Kōzai Yoshikiyo was holed-up, but, through the mediation of Kagawa Yukikage, Yoshikiyo surrendered to Chikakazu’s army. Bolstered by Yoshikiyo’s battalion of 1,000 soldiers, on 8/11, Chikakazu’s army totaling 11,000 troops departed from the Kokubun Temple (affiliated with the Uomuro faction of the Shingon sect) in Sanuki and surrounded Sogō Castle. At the time, Sogō Masayasu was in Shōzui Castle with Sogō Masayuki (an illegitimate son of Sogō Kazumasa) serving as the chamberlain to defend the castle. Nevertheless, upon receiving news of the siege by an army of over 10,000 soldiers, Masayuki anticipated a prolonged conflict, so he reduced the size of the garrison to 1,000 soldiers, stored three months worth of provisions, and prepared to hold-out against the besieging forces.
After their arrival in the environs of Hiraki, Chikakazu’s army cut-down the wheat crops and plowed under the rice nurseries. Owing to the destruction of crops by the large army, many of the residents were displaced and fled to their hometowns.
Next, Chikakazu’s army surrounded Sogō Castle from all four sides, and made roads to enable an assault on the castle. However, the garrison in the castle possessed a large stockpile of arquebuses, and by firing from turrets on all sides, brought to a halt the building of roads to the castle. The Chōsokabe army closed to within approximately 200 meters from Sogō Castle, deployed two cannons, and blasted the castle turrets. This made it difficult for the defenders to continue to hold the castle. At this moment, however, Maeda Munekiyo, the lord of Maeda Castle, launched a nighttime attack and protected the defenders of Sogō Castle. Through the use of ninja tactics, these Maeda’s forces hampered the besieging army. By launching nighttime attacks and using secret passages, they sneaked into Motochika’s base and stole food provisions as well. In a faraway location with dwindling provisions, the Chōsokabe army began to grow wary of the prospect of a long siege.
Meanwhile, beginning on 8/28 of Tenshō 10 (1582), Sogō Masayasu endured a siege of his base at Shōzui Castle by Chōsokabe Motochika, but finally agreed to a pardon on the condition that he vacate the castle, whereupon, on 9/21, he fled at night to Toramaru Castle in Sanuki. This is known as the Battle of Nakatomigawa. After entering Toramaru Castle, Masayasu requested reinforcements from Toyotomi Hideyoshi, noting in a letter that the rebels from Tosa were gradually gaining strength, threatening to take over Shikoku. Although he was holding on to his territory, the enemies needed to be subdued at an early date. If the situation were to persist, a calamity would occur. Hideyoshi responded by ordering Sengoku Hidehisa, the lord of Sumoto Castle in Awaji Province, to send reinforcements to Masayasu.
During that time, with respect to Sogō Castle, the Chōsokabe army departed from Iwakura, crossed the mountains, and converged with troops led by Kagawa Chikakazu, reaching a combined army of 36,000 men. The army laid siege a second time, but Sogō Castle did not fall. With the onset of the winter season, a unit was left to keep watch on the castle while the remainder of the Chōsokabe forces returned to Tosa and the First Siege of Sogō Castle came to an end.