Based on all criteria - military power, economic influence, cultural dominance - America remains number one, even though other, new players are increasingly challenging it in that role.

More recently his book The World America Made has been publicly endorsed by US President Barack Obama and its theme was referenced in his 2012 State of the Union Address. Robert Kagan (born September 26 1958 in Athens Greece) is an American historian author and foreign policy commentator at the Brookings Institution.