The renewed tensions between the United States and Russia, leading to a rapid diplomatic and military escalation between the two countries.
Some people claim it started in 1999 when NATO expanded to include former Soviet allies. Others pin the start date as August 8th, 2008, when Russian forces pushed the US allied Georgian forces out of South Ossetia and Abkhazia.
Quote by Russian President Medvedev, August 26th 2008:
"We are not afraid of anything, including the prospect of a new Cold War" (Cold War II)