Should the US miltary be used to prevent genocide?

Here is an interesting story from Sen. Barak Obama, a presidential candidate.

http://news.yahoo.com/s/ap/20070720/ap_on_el_pr/obama_ap_interview_9;_ylt=As4S17F7vF68zLgNqFzPtd0E1vAI

In this article, Obama says that preventing genocide is not enough of a reason to stay in Iraq. He goes on to point out other places in the world, like the Congo, where genocide is happening and the US has no presence.

The use of miltary force is complicated politically, and even more so when viewed from a Christian perspective. I understand Obama's point, and the US cannot prevent every atrocity. But by the same reasoning, Hitler was given free reign over Europe and over Jews. The movie Hotel Rwanda showed how the world did nothing as hundreds of thousands of people were slaughtered in Rwanda due to ethnic cleansing. It was terrible, and you look back and wonder how this was allowed to happen.

I pray that a slaughter of our own making does not ensue.