President Barack Obama made an emotional visit to the former Nazi concentration camp at Buchenwald, Germany, Friday, saying that the camp should serve as a reminder of humanity's duty to fight the spread of evil.

The visit had personal significance for the president, whose great-uncle helped liberate prisoners from the camp during World War II.

Obama told reporters earlier in the day that his great-uncle, Charles Payne, had a "very difficult time re-adjusting to civilian life" after helping his Army division liberate the Ohrdruf forced labor camp, a subdivision of Buchenwald