In just a matter of weeks, many of the world’s most powerful leaders and military advisors will descend on Chicago for the NATO summit.

But more than 60 years after the North Atlantic Treaty was signed and the organization was formed, big questions remain about the health and relevance of NATO in the 21st Century.

Last year, then-U.S. Defense Secretary Robert Gates blasted NATO members for not sharing more of the burden in funding and fighting, and said the organization was a two-tiered alliance consisting of some nations “willing and able to pay the price and bear the burdens of alliance commitments, and those who enjoy the benefits of NATO membership … but don’t want to share the risks and the costs.”

Add to that the end of the Cold War, the rise of the BRIC nations and the newly announced “Asian pivot” in U.S. foreign policy, and the question becomes: What role, if any, should NATO play in the 21st century?

We explore that question on the Afternoon Shift with Harvard University professor and former U.S. Ambassador to NATO, Nicholas Burns.

He’s joining hundreds of scholars and dignitaries in Chicago this week to discuss NATO’s reach and relevance during a three-day international conference hosted by the Chicago Council on Global Affairs and the Chicago NATO Host Committee entitled “Smart Defense and the Future of NATO: Can the Alliance Meet the Challenges of the 21st Century?”