Barack Obama's First New War

After weeks of apparent reluctance, the United States joined the UN's fight to protect Libyans against their leader, Moammar Gadhafi. President Obama promptly left for South America, saying that the intervention will be over for the US in a matter of days. When he returns, he'll have a lot of questions to answer, especially now that a US plane has crashed in Libya. The crew is safe, but Republicans and Democrats are asking, "What's the mission? Why wasn't Congress asked in advance?  How long will this go on?" Beyond that, is there an overall rationale for intervention in one country versus another? If Libya, why not Yemen, Bahrain or the Ivory Coast? Is there an overall strategy that also considers the impacts on Israel, Iran, North Korea and the roles of the UN and NATO?