In 1860 the U.S. military, Mexican-Americans, Zunis, and Utes all raided Navajo land. The Navajo killed four soldiers from Fort Defiance in January. On August 30, Manuelito, Barboncito and 1,000 Navajo attacked the US army in the Second Battle of Fort Defiance. Meanwhile, others raided sheep near Santa Fe. 400 New Mexicans under Manuel Antonio Chaves formed a militia and raided Navajo land, followed by independent raids by citizens to take captives. In retaliation for the attack on Fort Defiance, Canby's Campaign set out in early October. Over the next several months seven army expeditions killed 23 Navajo and destroyed Navajo stock and crops. In 1861, another treaty was signed at Fort Fauntleroy . Ft. Defiance was decommissioned on February 24. Raiding continued between groups of citizens and Navajo warriors. A dispute arose in August from allegations of cheating at a horse race between Navajo & New Mexican Volunteers forces at Fort Wingate, and Manuel Antonio Chaves of the New Mexico Volunteers ended up ordering his men to fire into the Navajo. This incident incensed the Navajo, and they raided the New Mexicans.
Question: What did the Navajo do that caused all the raids?
Answer: killed four soldiers from Fort | Defiance