Conversation so far:
Who is Red Cloud?
Red Cloud was one of the most important leaders of the Oglala Lakota.
When was Red Cloud in power of the Oglala Lakota?
Red Cloud was one of the most important leaders of the Oglala Lakota from 1868 to 1909

Question: Who did he attack?
Self-contained rewrite: Who did Red Cloud attack in Red Cloud's War?