Tianshui

The battle of Tian Shui is a battle between Wei and Shu. This battle was fought because of Jiang Wei who was a good general if under Shu's care. Historically and in the novel there wasn't any battle that happened in Tian Shui just a simple revolt. Also the battle isn't because of Jiang Wei but was a revolt by Zhuge Liang to capture the prefectures of Nan An, An Ding, and Tian Shui (which was pacified by Zhang He later on).

In The Games
In the Dynasty Warriors series the battle's purpose was just like the novel: for Jiang Wei to defect to Shu. In the fifth installment while playing the side of the Shu forces the player needs to defeat Xiahou Mao and Cui Liang to capture Nan An and An Ding. Zhuge Liang will order his men to release Xiahou Mao inside the Tian Shui Castle telling the commander, Ma Zun, that Jiang Wei has defected. This would be the time that Jiang Wei will return to Tian Shui. Defeating him would start Ma Zun's retreat if the player defeats him then the battle has won. In the Wei side, the player needs to rescue Na An or An Ding from the invaders. If successful, the battle will be an easy win. If the two castles fall Ma Zun will attempt to retreat and will be confused leading him to Zhuge Liang's main camp. If the player defeats Zhuge Liang the battle will be finished. The battle was removed in the sixth installment with Jiang Wei.