Kusegawa

The Battle of Kusegawa (杭瀬川の戦い), also called the Battle of Kuzegawa, is the first known clash between the Western and Eastern armies with the main commanders of each faction. Taking place on the day before Sekigahara, it is usually noted as a skirmish rather than a battle due to the low number of troops involved. This is pretty much ignored in the games.

Samurai Warriors
In this series, this place shares the same map as Tedorigawa except that it takes place during the daytime hours and is sunny. In each of its appearances, the main goal of the conflict is to boost morale for either army.

Samurai Warriors 2 allows players to control either the Western or Eastern armies for the conflict. During the Western side of the battle, the player cannot allow a single ally officer to be routed. Mitsunari stands guard of the main camp while Sakon coordinates the army's offensive. He orders the troops to defeat the Eastern generals on the frontline and prevent their escape. Around the same time, players are also asked to defeat Yoshimasa Tanaka and Kojirō to stop them from creating an escape path in south-eastern corner of the map. Their time to complete the second mission is limited so players are asked to hurry. As the battle lengthens, Tadakatsu and Ina appear to reinforce the stranded Eastern generals. Hanzō also appears to endanger the main camp. Players need to defeat every enemy officer on the map in order to achieve victory. The battle remains relatively the same in the Xtreme Legends version, save for Motochika's addition into the Western army's ranks.

For the Eastern side of the battle, players need to rescue at least one stranded general in order to achieve victory. This requires the task of hurrying to the frontline generals and escorting them to the eastern bank, fighting through several Western army generals along the way. Tadakatsu, as the leader of the Eastern troops, needs to additionally survive the conflict. If the players choose to save the generals this task, Tadakatsu will regroup the army and order a full-scale assault. They will claim victory once they have defeated Sakon.

The Samurai Warriors 3 version of the battle omits Yoshihiro as a participating general and keeps Motochika. It's also a battle that only occurs for the Western army.

Warriors Orochi
After subduing heroes from the Three Kingdoms period and the Sengoku Jidai period, Orochi is deemed the ruler of the new world in Warriors Orochi. With Wei having lost Cao Cao in battle, Cao Pi submits to Orochi's forces. As his first task under Orochi, Da Ji orders the Cao heir to deal with the insurgents against Orochi's reign. Cao Pi obeys with his remaining loyal generals, Xu Huang and Zhang Liao. Da Ji protects the ally main camp at Kusegawa while Mitsunari directs their army's course of action.

Cao Pi is ordered to deal with the rebels lead by Zhang Jiao in the northern part of the map. Mitsunari uses Cao Pi's attack as a distraction for an attack on the enemy main camp. After Zhang Jiao falls, Huang Gai, the leader of the anti-Orochi rebels, presses his forces to attack. Mitsunari is suspicious of the southern garrison and waits for the generals inside it to rush towards the ally main camp. Defeating them triggers his march towards Huang Gai's position using the southern path. Cao Pi and his army will continue to make their way towards the enemy camp from the north-western path. When either army comes close to the enemy main camp, Xiahou Yuan arrives to reinforce Huang Gai. The archer general retreats after his defeat and is disappointed with Cao Pi's allegiance to Orochi. Xu Zhu guards the gate for the enemy main camp and needs to be defeated for it to be opened. Once Huang Gai is routed, Cao Pi spares him and frees the Wu general. Xu Zhu will thank Cao Pi for the food and joins Wei.

Kessen
Kusegawa is the first battle and the tutorial for first time players in Kessen. Both armies spot one another across the fog, hesitant to act for fear of an ambush. Undeterred, Ieyasu sounds the horn for battle and races at the chance to take Mitsunari's head.

Each army rides with limited numbers and lead a total of three generals into battle. The Western army has Sakon and Gamo beside Mitsunari at the start; Ieyasu has Honda and Ii by his side. Reinforcements can come later into the conflict for either side, each general appearing from the ends of the map. Akashi sides with the west and Fukushima assists the east. The battlefield is a tiny location compared to other conflicts, making battles between either armies inevitable. If the players follow the tutorial, they will fight as Ieyasu and will lose Honda to Mitsunari's cannons. However, they will weaken Mitsunari's army by striking down Gamo.

The player is free to win or lose the skirmish as the results do not alter their battle history. However, the consequences of the player's choice does slightly change officers' allegiances for either side.

Historical Information
A few days before October 21, 1600, Ishida Mitsunari and his troops were stationed at Ogaki Castle. They were evaluating their situation when Tokugawa's army arrived two days later at Mino Akasaka, a few miles away from their location. Seeing the massive army before them, many of the Western army soldiers began to quiver with fear. It is said that even Mitsunari was frightened by the sight.

One man who wasn't afraid was Shima Sakon. Wanting to restore the spirit of the men, he requested permission to lead a handful of men to test the enemy's skill. His request was wearily granted and he rode out with 500 men to the river dividing the two armies, Kusegawa. Akashi Teruzumi, who had at least 800 men, supported him by waiting in ambush. Hiding his troops in the nearby thicket, Sakon attacked the nearest general, Nakamura Kazuhide. Lured by the offense, Kazuhide and his closest allies, Arima Toyouji and Noisshiki Sukeyoshi, followed the retreating Sakon. As they pursued him, they were ambushed and fought blindly in the forest. Honda Tadakatsu, who noticed the ruckus, immediately ordered his comrades to retreat and they obeyed. Sakon and Teruzumi triumphantly returned and their army's morale was restored. Based on his experience on the field, Sakon advised to move the battle to Sekigahara.

In retrospect, most historians consider this a victory of sorts for the Western army. Though there were losses on both sides, they were minimal. The unit with the highest reported casualties was Sukeyoshi who lost 40 men in the assault. Even so, the impact of the skirmish is relatively minor in the larger scope of the war. A popular folktale says that Ieyasu casually watched the entire battle from Akasaka while eating his lunch; he didn't even bother to try to don his armor.

Today, Ogaki Castle is a museum for Sekigahara and is considered a national treasure in Japan.