Peru and Chile have a rivalry that dates back from the War of the Pacific. Previously, the two nations had been great friends and allies; but all that "love" was soon turned to "hate" during the war. The point of conflict comes from the Peruvians claiming Chile raided Lima and oppressed and mistreated the Peruvians during their occupation of Peru, and from Chile claiming Peru broke the friendly relations of both nations by not standing neutral in the Chile-Bolivia conflict.
The problem from the war soon turned into sports competition, specially football since that is the favorite sport of both nations. The Chile vs. Peru games generally tend to be very competitive and at times rough. Nevertheless, it is certainly one of the most competitive classics of the South American continent for both teams give it their all.