Dennis Jett: what's stopping Trump from pressing the button?

What are the checks and balances with regard to US president Donald Trump and the enormous US nuclear arsenal? Dennis Jett is a founding member of the School of International affairs at Penn State, and a former career diplomat serving 28 years in the State Department. He is a member of the Council on Foreign Relations and American Academy of Diplomacy. He explains the processes that need to occur before any button gets pushed.