Siege of Akasaka

What Happened

The siege of Akasaka was fought from 1331-10-13 to 1331-11-21 at Shimo-Akasaka Castle, a fortress on Mount Yoshino in what is now Osaka Prefecture. The castle stood in the former Kawachi Province, and the siege formed part of the opening campaigns of the Genkō War, the armed struggle between Emperor Godaigo and the Kamakura shogunate.

The fortress was held by forces loyal to the emperor, including Kusunoki Masasue, who fought alongside his more famous brother Kusunoki Masashige. The shogunate’s army besieged the castle for roughly five weeks before it fell. The siege ended on 1331-11-21, and the shogunate’s victory at Akasaka was followed by the siege of Chihaya, where the imperial forces made their next stand.

Background

By 1331, the Kamakura shogunate had ruled Japan for nearly 150 years, but its authority was fraying. The Hōjō clan controlled the shogunate from behind the scenes, while the imperial throne in Kyoto had become a figurehead institution. Emperor Godaigo, who took the throne in 1318, refused to accept this arrangement and began plotting to overthrow the shogunate and restore direct imperial rule.

The Genkō War broke out in 1331, the first year of the Genkō era. Godaigo’s plans were discovered, and the shogunate moved against him, but the emperor escaped Kyoto and rallied supporters in the provinces. Among those supporters was the Kusunoki family, based in Kawachi Province, who built a network of mountain fortresses to resist the shogunate’s larger armies. Shimo-Akasaka Castle was one of those strongholds, positioned on Mount Yoshino to control the surrounding approaches.

The shogunate dispatched a substantial force to reduce the castle. The defenders, though outnumbered, used the mountain terrain to hold out for over a month. The siege was one of the first sustained engagements of the war, and it set the pattern for the guerrilla-style resistance that the Kusunoki forces would employ throughout the conflict.

Why It Mattered

The siege of Akasaka demonstrated that the shogunate’s military machine could be checked, even if only temporarily, by determined defenders using fortified mountain positions. The month-long resistance at Shimo-Akasaka gave Godaigo’s cause credibility and bought time for other imperial loyalists to organise.

The fall of the castle did not end the war. The imperial forces simply withdrew to the nearby fortress of Chihaya, and the siege of Chihaya followed almost immediately. That second siege would prove even more costly for the shogunate. The resistance at Akasaka, though a tactical defeat, contributed to the broader strategic picture: the shogunate could not crush the rebellion quickly, and the war dragged on until the shogunate collapsed in 1333.

For the Kusunoki family, the siege established their reputation as the emperor’s most steadfast military supporters. Kusunoki Masasue’s participation at Akasaka placed him in the front rank of that loyalist tradition, a status that later chroniclers would magnify.

The Name in Japanese

The Japanese name for this event is 赤坂城の戦い, read in kana as あかさかじょうのたたかい, and in romaji as Akasaka-jō no Tatakai. The name translates literally as "Battle of Akasaka Castle."

Breaking it down character by character:

• 赤 (あか, aka) — "red." This is the first character of the castle’s name.
• 坂 (さか, saka) — "slope" or "hill." Together, 赤坂 (Akasaka) means "red slope," the name of the location.
• 城 (じょう, jō) — "castle." In this compound it takes the reading jō, and it marks the structure at the centre of the battle.
• の (no) — a possessive particle, written in hiragana. It connects the castle to the battle, giving the sense "of" or "at."
• 戦い (たたかい, tatakai) — "battle" or "fight." The character 戦 carries the core meaning of war or combat, and the okurigana い completes the reading.

The full name thus reads "the battle of Akasaka Castle." Note that the castle is sometimes called Shimo-Akasaka Castle (下赤坂城, Shimo-Akasaka-jō), where 下 (shimo) means "lower," distinguishing it from an upper fortress in the same area. The siege name, however, uses the shorter form.

Key Figures

Kusunoki Masasue (楠木正季) was a warrior of the Kusunoki clan and a participant in the siege. He fought at Shimo-Akasaka Castle as part of the imperial loyalist forces. Historical records give him a role in the defence, though the details of his actions at Akasaka are sparse. He would later die alongside his brother at the battle of Minatogawa in 1336, cementing his place in the loyalist legend.

Emperor Godaigo (後醍醐天皇) was the reigning sovereign and the leader of the rebellion against the Kamakura shogunate. Though not present at the siege, the castle was held in his name, and the resistance at Akasaka was a direct consequence of his decision to take up arms in 1331.

The Kamakura shogunate — the besieging force — is not identified by a single named commander in the surviving record of this siege. The shogunate’s army was drawn from the Hōjō-controlled military apparatus that had governed Japan since the late 12th century. Its failure to take the castle quickly was a sign of the regime’s declining effectiveness.