When should states intervene militarily to stop atrocities in other countries? The question is an old and well-traveled one. Indeed, it is now visiting Syria. In 1904, U.S. President Theodore Roosevelt argued that “there are occasional crimes committed on so vast a scale and of such peculiar horror” that we should intervene by force of arms. A century earlier, in 1821, as Europeans and Americans debated whether to intervene in Greece’s struggle for independence, President John Quincy Adams warned his fellow Americans about “going abroad in search of monsters to destroy.” More recently, after a genocide that cost nearly 800,000 lives in Rwanda in 1994, and the slaughter of Bosnian men and boys at Srebrenica in 1995, many people vowed that such atrocities should never again be allowed to occur. When Slobodan Milosevic engaged in large-scale ethnic cleansing in Kosovo in 1999, the United Nations Security Council adopted a resolution recognizing the humanitarian catastrophe, but could not agree on a second resolution to intervene, given the threat of a Russian veto. Instead, NATO countries bombed Serbia in an effort that many observers regarded as legitimate but not legal.
Nye, Jr., Joseph S. "In a Brutal World, a Responsibility to Protect Will Stay on The Table." Daily Star, June 13, 2012.