The battle of Karasaki Beach (October 1331) was the first battle of the Genko War (1331-33), and saw the Monastic supports of the Emperor Go-Daigo defeat a cavalry force sent to capture him.
Since coming to the throne in 1318 the Emperor Go-Daigo had prepared to make an attempt to overthrown the Kamakura Shogunate and restore direct Imperial rule. During 1331 the agents of the Shogunate discovered part of this plan, and in late September the Bakufu (a term for the collective officials of the Shogun) dispatched two officials to Kyoto, where they were to take the Emperor into exile and kill Prince Morinaga, his most able son, and an abbot of the Buddhist monastery of Enryaku-ji on Mount Hiei (home of a powerful force of warrior monks).
News of this plan reached the Prince, who passed the news to his father and suggested a way to take advantage of the situation. While the Emperor himself escaped in secret one of his officials, dressed in the Imperial costume and using the Imperial litter, would leave the city very publicly and head towards the monastic complex on Mount Hiei. The Prince hoped that the Bakufu would respond by sending an army to try and capture the Emperor, a move that would almost inevitably trigger a battle between the troops of the Shogunate and the monks.
The Prince's plan was partially successful. In early October 1331 the Emperor escaped from Kyoto and headed south towards the southern capital at Nara. In the meantime Lord Morokata, one of the Emperor's senior advisors, put on the imperial dragon robes and made his way to the Western Pagoda cloister on Mount Hiei. The fake imperial party then announced their presence, and announced that the Emperor had entrusted himself to the temple. A sizable army soon assembled at Mount Hiei, made up partly of warrior monks from the temple and partly of warriors from the surrounding areas. Prince Morinaga was also present, (although only commanded part of the Imperial army) as was one of his brothers.
Not everyone at Hiei supported the Emperor. One monastic official, Jorimbo, sent a message to the Rokuhara informing them that the Emperor had reached the monastery, had the support of 3,000 monks and was planning to attack Rokuhara. Jorimbo suggested that the Bakufu should send a force to the eastern slopes of Mount Hiei to attack the Emperor's supporters. He would then attack from behind, trapping the Imperial supporters between two armies.
After checking the palace to see if the Emperor had indeed fled, the Rokuhara decided to send two columns towards Mount Hiei. According to our main primary source, the Taiheiki, the Bakufu sent 5,000 horsemen to attack Mount Hiei from the south, going via Sagarimatsu and Mount Seki, and another 7,000 horsemen who would advance further east, towards Otsu, the western shores of Lake Biwa, and then north up the coast towards Karasaki, east of Mount Hiei. According to the same source the Imperial loyalists had 6,000 cavalry who had gathered at Mount Hiei overnight and the 3,000 monks.
The battle began when the Imperial troops at Sakamoto, east of Mount Hiei, detected the Bakufu force advancing towards Karasaki. A small force of 300 monks rushed down to the beach to confront the advancing cavalry. Although the monks were badly outnumbered, they were handed an early success when one of the Bakufu commanders, Kaito Sakon Shogen, decided to try and defeat the monks before reinforcements arrived. He charged into the small force of monks but was killed by Kaijitsu of Harima, one of the monks. In the aftermath of this fight Kaito's young son attempted to avenge his father. Kaijitsu attempted to capture him alive, but the son was killed by reinforcements. Kaito's thirty-six close retainers then charged into the fray, hoping to be killed, but they were forced away.
More men were now fed into the battle. Three hundred Bakufu cavalry attacked the monks, who were reinforced by fifty fresh men. The battle took place on a narrow road between the beach and some rice fields, so the Bakufu forces were unable to take advantage of their numbers.
The main Imperial forces now began to move. Some men got into boats to the north of Karasaki and attempted to reach Otsu, behind the Bakufu force. Prince Morinaga advanced with his 3,000 men and another 7,000 monks came down from the main cloister on Mount Hiei.
Facing with the prospect of being surrounded, the Bakufu forces decided to retreat. They were harassed by archers while they pulled back, and a significant number of important retainers were killed.
In the aftermath of the fighting the monks discovered the ruse that the Emperor had used to escape from Kyoto. The monks of the main cloister demanded that the Emperor move there from the West Pagoda. The monks of the West Pagoda agreed, but when they went to inform the Emperor they discovered Morokata in his place. This discovery greatly discouraged the monks and encouraged the supports of the Bakufu in the monastery. The Princes and the main Imperial advisors soon felt endangered and fled from the area. The Princes soon split up and headed into different areas. Prince Morinaga went on to play a major part in keeping his father's cause alive over the next two years.
The defeat of the Bakufu forces at Karasaki did have some long term impact, encouraging the monks at Kasagi to support the Emperor, as did a number of warriors from nearby provinces. This force wasn't enough to successfully defend Kasagi against the inevitable siege, but it did show that the Emperor had support.