Suruga

Suruga was the domain of Yoshimoto Imagawa. After his death, it sparked a local civil war where the Tokugawa, Takeda and Hojo forces all scrambled to seize the territory in a series of skirmishes from the far less capable successor, Ujizane Imagawa. The territory mostly fell into Ieyasu Tokugawa's hands while Ujizane was allowed to leave in peace, thanks to Yasutomo Asahina's stalwart protection and loyalty to his lord.

Role in games
In Samurai Warriors 3, an earlier conflict takes place when Yoshimoto Imagawa is still alive at Suruga-Sagami. Ujiyasu Hōjō launches a pre-emptive strike on his brother-in-law and Shingen Takeda assists Yoshimoto in this battle. The Uesugi also appear as third party forces in the battle to observe. Defeating Kotarō Fūma who jokes about the chaos caused by the conflict, actually causes Shingen to acknowledge his point and sue for peace between the kanto daimyo. Ujiyasu's side is much the same, though the Takeda are far more of a threat than the Imagawa, with Shingen's reinforcements consistently threatening the Hojo forces. A more accurate viewpoint of the conflict takes place with Kenshin Uesugi and Aya's stories. They rescue Yoshimoto at Suruga from a combined Takeda and Tokugawa coalition, trapping the allied forces in a pincer. Defeating Ieyasu in the south leads the Tokugawa forces to withdraw, allowing the army to keep their sole focus on Shingen. The Imagawa are further bolstered by the arrival of Ujiyasu on the allied side, prompting a charge on Shingen. Despite the victorious outcome of this battle, Yoshimoto succumbs to death shortly afterwards.

Samurai Warriors 4 has two distinct conflicts for Suruga. The first being at Enshu and the other being at Kakegawa Castle. Enshu references the Takeda's attempts to take Suruga from a Imagawa-Hojo alliance. They advance on two sides, prompting the defection of many Imagawa retainers, and cut off Ujizane's escape to the south. Once defeating Ujizane, the player can advance to Ujiyasu's garrison in the east to complete the job. The Hojo-Imagawa side requires a lot of cleanup of an overzealous frontline and many defecting allies. Escorting Ujizane to the escape point must be done, and in order to reverse the tide, a sneak attack on the Takeda main camp is required. Shingen foresaw this as he charges and leaves Nobuyuki Sanada and Katsuyori Takeda in charge of his main camp. Once the player breaks through them however, they can pincer and defeat Shingen to ultimately finish the battle.

Kakegawa castle is the scenario where the Tokugawa attack. Again, they rely on many defecting Imagawa retainers to force their way in and use Ujizane as a hostage to force the Hōjō and Kai to open the remaining way of defenses out of anger. After the battle, Ieyasu and Ujiyasu launch an agreement whereby Ujiyasu will let them have Suruga, if they hand Ujizane over to him. The Hojo battle plays out similarly, where Tokugawa forces launch waves of attacks on the castle, sapping the Imagawa's morale and causing many defections. The outcome of the battle between the two parties remains the same, even after Ieyasu's defeat as Ujiyasu realises that Ujizane is not a man suited for war but for peace. Naotora Ii ironically serves both sides in this case, when playing as Tokugawa or Hojo, she is present as an ally. Samurai Warriors Chronicles 3 also references an event where Tazu Iio meets her demise at Enshu at Naotora's hand.

Historical Information
Inn the 1550s, both the Takeda, Hōjō, and Imagawa clans began to achieve enough stability that they began to eye one another's land. In 1552, the Takeda and Imagawa entered into an alliance by marrying Yoshimoto's daughter to Shingen's eldest son, Takeda Yoshinobu. Fearing this alliance, Hōjō Ujiyasu moved against Imagawa Yoshimoto in July, 1554, bringing their new allies the Uesugi along for support. However, the two warlords combined their strength and pushed Ujiyasu back. With no one clan wanting to commit too much and loss too many soldiers, a new, triple alliance was proposed. This multi-layered allaiance was solidified with the marrage of Ujiyasu's daughter, Lady Hayakawa, to Imagawa Ujizane and Shingen's daughter, Obaiin, to Ujiyasu's son, Hōjō Ujimasa.

In 1560, Yoshimoto was slain and the Imagawa's strength began to fall quickly. This weakness was compounded in 1563 when the Matsudaira clan decalred independence under Ieyasu's leadership. With less then half their strength remaining, Shingen put the final nail in the triple alliance by disinheriting his eldest son and sending back his wife to the Imagawa in 1567. By 1568, Shingen was posed to begin the second invasion of Suruga. He invited the Hōjō to join in his assult, but they declined.

Initially Shingen found little resistance, with quite a few Imagawa officers changing sides due to low loyalty for their lord. He even managed to reach Sunpu castle, driving out Imagawa Ujizane. The Hōjō rallied their soldiers and rushed to Ujizane (and Lady Hayakawa)'s rescue, stopping the Takeda's advance to enable the failing Imagawa leader to escape into their protection.