Tragedy of Yosuga Pass

The is an event that happened ten years prior to the start of the Fourth Shinobi World War.

Background
Three shinobi from Kirigakure, Suiren, Ganryū and Junsai were sent on a mission to retrieve a document taken by Kumogakure with Iwagakure's assistance. However, when the document was retrieved, the Iwa shinobi immediately betrayed the Kiri team on the orders of their Tsuchikage. This resulted in Junsai's death and Suiren sacrificing herself in order to save Ganryū at Yosuga Pass. Since that day, Ganryū and other Kiri ninja who disapproved the betrayal had grown to despise Iwa and it's shinobi. This incident, known as the Tragedy of Yosuga Pass marked the beginning of hostility between Kirigakure and Iwagakure. This event would later be forgiven after the Third Tsuchikage delivers Suiren's stolen bangle to Kirigakure, in hopes of amending their weak relationship before the War.