The Battle of Onogawa was a major battle fought between the Shimazu and Tsuchimochi clans of Kyushu in September 1546 along the Ono River. The Shimazu clan decisively defeated the Tsuchimochi army (despite its superior technology), slaying the clan's daimyo Chikashige Tsuchimochi, annihilating his army, and breaking his clan's military might. The Shimazu victory at Onogawa enabled the Shimazu to finish off the weakened Tsuchimochi clan and reverse the prevalence of Christianity in northeastern Kyushu.
Background[]
By the start of 1546, the Buddhist Shimazu clan of Satsuma Province had become the most powerful clan in southern Kyushu, allying with the Sagara clan to the northwest to secure its flank. At the same time, the Tsuchimochi clan of northern Kyushu steamrolled the Otomo clan and other clans in the northeast to become the dominant power in northern Kyushu. The Tsuchimochi clan consolidated its gains by converting to Christianity, the religion prevalent among the Otomo clan's former subjects.
The Shimazu army at Onogawa
In January 1546, the Shimazu clan preemptively attacked the Tsuchimochi clan in Hyuga Province on Kyushu's eastern coast, capturing Hyuga and Taketa and advancing up to the Ono River, which splits present-day Oita Prefecture in half. Across the Ono River lay Funai Castle, the administrative center of Bungo Province and the castle of Tsuchimochi. During the summer of 1546, Chikashige Tsuchimochi and his right-hand man Chikaie Takanashi marched the Tsuchimochi clan's 2,677-strong army south from northern Bungo Province to confront the Shimazu clan's large army, led by Tomokata Tanegashima. The actions of the Shimazu clan's ninja, Korehisa, sabotaged Tsuchimochi's army and bought time for Takahisa Shimazu to march his smaller army north to garrison Oka, from which he could reinforce Tanegashima's army, which took up a defensive position a few miles south of the Ono River bridge.
Battle[]
Dispositions[]
Tomokata Tanegashima giving a speech to his army
In September 1546, Chikashige Tsuchimochi led his 2,677-strong army across the Ono River to attack the Shimazu army and break the deadlock. Unbeknownst to Tsuchimochi, Takahisa Shimazu's army was within marching distance of the battlefield, boosting the Shimazu's army to a combined strength of 2,983 troops.
The Shimazu army formed up in a line which gave their archers cover in separate treelines, with their spearmen protecting the gaps between the forested hills, and their yari cavalry taking up a position in the thickly-forested area on the army's right flank. Tanegashima was aware that the Tsuchimochi clan had taken advantage of its Christian faith to obtain arquebuses from its Portuguese trade partners, so he sought to use the trees as cover from the Tsuchimochi riflemen's bullets.
Meanwhile, Takahisa Shimazu led his contingent to form an angled left flank of the Shimazu army, hoping to outflank the Tsuchimochi force.
Battle[]
The melee fighting at Onogawa
The battle began when the Tsuchimochi army began its advance and deployed its arquebusiers to skirmish with the Shimazu army. The Shimazu archers traded volleys with the Tsuchimochi riflemen, and the main body of Tsuchimochi troops began to break up into subgroups to attack the Shimazu army in detail. The Shimazu responded in kind, and it was then that Takahisa ordered his flank of the army to assault the Tsuchimochi clan's vulnerable right flank. The Shimazu right flank also emerged from the forest to outflank the Tsuchimochi left flank, and, as Takahisa inspired the Shimazu troops on the left flank, Tanegashima rallied the troops on the right flank. The Tsuchimochi left was the first to break, and Chikaie Takanashi was slain as he attempted to rally the troops on that front. The Shimazu soon routed the Tsuchimochi right flank, and the Tsuchimochi center would soon find itself attacked from both sides.
The Tsuchimochi retreating from Onogawa
The Tsuchimochi army began to break, and its routing remnants were chased down by the Shimazu generals' hatamoto bodyguards and their yari cavalry, while Chikashige Tsuchimochi decided to suicidally charge into battle with the Shimazu spearmen in one last act of bushido; he was promptly cut down. The Tsuchimochi army was annihilated, destroying the might of the Tsuchimochi clan and confirming the Shimazu clan's hegemony over northeastern Kyushu.
Aftermath[]
The dead at Onogawa
The Battle of Onogawa had long-lasting ramifications for the future of Kyushu. The Tsuchimochi clan, which had become a bulwark of Christianity in Japan, was essentially destroyed at the Battle of Onogawa, and the 324 remaining soldiers of its main army were butchered by the Shimazu army in October, with the Shimazu suffering just 72 losses in the process. The Shimazu were then able to advance on Funai, which fell to them with just 40 losses. The Shimazu chose not to revive their old rivals, the Otomo clan, instead occupying the province. Takahisa Shimazu, anticipating unrest in the province because of foreign religious influences, torched the nanban ("southern barbarian"; Portuguese) trading port, leading to a gradual reversion of the province's population to Shinto-Buddhism.