The state of the UN as it turns 80

The United Nations came into existence 80 years ago, as its charter came into force. It was founded as an effort to avert another world war in the aftermath of Germany's surrender.

Arguably, it has succeeded so far, but with many member nations flouting rules and weakening their support, is the organization now at one of its most vulnerable moments?

For more on the state of the UN, its founding and why it is still vital to global peace efforts, host Scott Tong speaks to Margaret MacMillan, professor emeritus of international history at Oxford University and author of the book "War: How Conflict Shaped Us."