The siege of Chihaya (March-22 June 1333) was the turning point in the Genko War (1331-33). The Shogunate's failure to capture the castle meant that their main army was pinned down, encouraged pro-Imperial revolts around Japan and forced them to commit ever more troops to the fighting. When the commander of one of these armies changes sides the Shogunate didn't have the resources to defeat him, and their position in central Japan collapsed.
Ever since coming to the throne the Emperor Go-Daigo had been preparing for an attempt to overthrow the Shogunate and restore direct Imperial rule. In 1331 the Shogunate had discovered one of his plots, and had decided to send him into exile. The Emperor escaped from Kyoto but was captured after the siege of Kasagi (3-31 October 1331). He was sent into exile, but his supporters continued to fight on. The Imperial family was represented by Prince Norinaga, while Go-Daigo's most successful supporter was a middle ranking warrior called Kusunoki Masashige. During 1332 Kusunoki Masashige recaptured his own castle at Akasaka, while the Prince issued calls for support. The Shogunate responded late in 1332 by moving a massive army to Kyoto, with the intention of defeating Kusunoki Masashige and removing the focus for the revolt.
This massive army was split into three columns. One was sent straight towards Mount Kongo. The second besieged Akasaka (18 February-c.14 March 1333) and the third besieged Yoshino Castle (March 1333). These two castles fell after short sieges, and the besieging forces moved to join the troops already at Mount Kongo.
Their new target was the castle of Chihaya. Our main source for this siege is the Taiheiki, a romantic history that tends to exaggerate numbers and probably over-dramatizes the course of events, but that is probably a reasonably reliable guide to the overall course of events.
The Taiheiki describes Chihaya as being guarded by deep chasms to the east and west and by the high steep peaks of Mount Kongo to the north and south. The castle itself was less than a league around, only seven hundred feet high (one assumes this refers to the natural terrain rather than the actual fortifications), and was guarded by fewer than 1,000 men, led by Kusunoki Masashige.
The Taiheiki's tendency to exaggerate numbers is at its most extreme when describing the size of the Shogunate's army. The first column to arrive is said to have been 800,000 strong and when the second and third columns arrived the total force rose to one million men! All we can really take from these figures is that the Shogunate's army was very large (perhaps 100,000 strong) and the besiegers were badly outnumbered.
Akasaka and Yoshino fell during March 1333. The Shogunate's full army was thus united at Chihaya in mid-March. The first assault may already have been made by this time and was a product of overconfidence. The attackers advanced towards the walls, protected only by their shields. The defenders threw rocks onto them from the castle walls, smashing the shields and exposing the attackers to their arrows. The Taiheiki records that 5,000-6,000 of the attackers were killed or wounded in this attack and that it took twelve scribes three days to write down their names. After this setback the besiegers decided not to risk another assault and instead prepared for a longer siege.
Their next move was to try and cut the castle's water supplies. A force of 3,000 cavalry commanded by the head of the Nagoya family was posted by the stream that appeared to be the castle's source of water, but in fact Chihaya was built around a mountain spring, and Kusunoki Masashige had made sure that there was plenty of water stored within the walls. After some time the troops guarding the stream relaxed, and at that point Kusunoki attacked them with 300 infantry, capturing their banners and driving them away before retreating to the castle. On the next day five thousand Nagoya troops attempted to attack the castle and regain their family honour, but the defenders rolled ten tree trunks down the slope killed 400-500 and forced the rest to retreat.
After this second attack the attackers decided to starve out Kusunoki Masashige and his men. The attacking troops were soon bored. Their commanders brought in teachers of poetry and work began on a poem with 10,000 stanzas. The troops also amused themselves with games and tea judging. These amusements didn't go entirely smoothly, and two leaders of the Nagoya are reported as having killed each other in a dispute over a backgammon game.
The defenders of the castle were equally bored, but according to the Taiheiki lacked all amusement. Kusunoki decided to provide some entertainment by tricking the besiegers. One night had twenty or thirty dummies built. These were clad in armour and armed, and were set up outside the castle, partly sheltered by some trees. The next morning five hundred men posted some way behind the dummies let out a battle shout. The attackers saw the dummies, heard the battle shout and assumed that the defenders had decided to come out of the castle and offer battle. Some of the nearest besieging troops advanced up the hill towards the castle, all eager to be first into battle. The 500 men fired a few arrows and then retreated into the castle. Just as the attackers were about to reach the dummies Kusunoki dropped fifty boulders from the castle, killing 300 and wounding 500. Only now did the attackers realise they had been tricked. They retreated to their camp, where they were mocked by their colleagues.
All of these events are said to have taken place before the 4th day of the 3rd month of the year (the third year of Genko), 20 March 1333. On this day a message arrived from the Shogunate ordering the army not to 'pass the days vainly without fighting'. At this point the dates given in the Taiheiki don't entirely work - the commanders of all three columns are said to have been at Chihaya before the attempt to cut off the water. Akasaka is said to have fallen on or about 14 March, and Yoshino either some days later (the fall of Akasaka is said to have motived the final attack) or some weeks earlier (according to the dates in the Taiheiki).
Whenever it arrived this message triggered another attack on the castle. This time the army's leaders decided to try and bridge one of the ravines that protected the castle on the west and east. A bridge five yards wide and more than sixty five yards long was built, and was pulled into place by two or three thousand ropes. A force of five or six thousand men was formed to cross this bridge (not bad for a bridge that was only 325 square yards in area!). This force was crossing the bridge when the defenders pumped oil onto it and set it on fire. In the crush the attackers were unable to escape, and thousands were killed when the bridge collapsed into the ravine.
The besiegers were now being harassed by guerrilla fighters led by Prince Norinaga. He had around 7,000 men who he used to cut the supply routes to the besieging army. As supplies ran out some of the attackers began to desert, returning to their homes. Many of these deserters were attacked and killed by the Prince's men as they attempted to escape. Other contingents left after their lord was killed or injured, and again according to the Taiheiki the number of men involved in the siege dropped from its starting point of 800,000 down to only 100,000.
One of the leaders to desert was Nitta Yoshisada, who would become a key figure in the fall of the Shogunate. He arranged to receive an Imperial Mandate from Prince Norinaga, but instead received a mandate direct from the Emperor. This was dated to the eleventh day of the second month of the third year of Genko (25 February 1333), suggesting that he was already in contact with the Emperor before reaching the area of Mount Kongo.
The Bakufu made one more attempt to capture Chihaya. The successful commander Utsunomiya was sent with 1,000 fresh riders. For a week his men launched a series of attacks on the castle again without success. They had more success in their attempts to undermine the castle, causing one tower to collapse, but the terrain was too difficult for their mining efforts to achieve much more.
The siege dragged on while the outcome of the civil war was decided elsewhere. Eventually the Bakufu general Ashikaga Takauji changed sides, advanced on Kyoto, and on 20 June captured the city. The surviving Rokuhara leaders attempted to escape east with their candidate for Emperor, but were soon surrounded. At the same time messengers were sent south to Chihaya, arriving at around noon on the day after the fall of the Rokuhara. The besieging force was still very large (the Taiheiki says 100,000 strong), but its leaders realised that their position was now hopeless and decided to try and retreat across the mountains towards Nara, from where they might be able to escape to the east.
The leaders of the retreating army reached Nara safely, but many of their men were killed by Imperial supporters as they attempted to cross the mountains. Most of the surviving commanders were captured and executed, while their men changed sides. The long siege of Chihaya had been a major drain on the strength of the Bakufu, and played a major part in their eventual downfall.