The threat to NATO is real, warns General Sir Roly Walker, head of the British Army, citing "serious challenges" ahead as concerns grow over a potential Russian attack in the coming years.
Speaking at the Royal United Services Institute (RUSI) on May 28, Walker stressed the urgency to act quickly, saying, "The biggest challenge we face is simply a lack of time."
NATO officials have raised alarms about Russia’s threat level, especially after a possible Ukraine ceasefire that could free up large Russian forces.
Indeed, the relationship between NATO and Russia is in deep crisis. In fact, the once cordial partnership between the North Atlantic Treaty Organization and the Russian Federation is at its lowest since the dark days of the Cold War. NATO leaders believe Russia poses a direct threat to the alliance, but their collective condemnation is falling on deaf ears in Moscow.
So, how has a previously constructive relationship between NATO and Russia turned so fractious? Click through this gallery and find out more about why Russia fell out with NATO.