Following a Russian drone incursion into its airspace on September 10, Poland has activated NATO's Article 4 to formally begin consultations with its allies. This unprecedented move came after Polish and allied forces shot down several Russian drones.
Poland declared the drone incursion an "act of aggression" and, in coordination with its NATO partners, shot down more than 10 drones. The incident forced temporary closures of major airports, including Warsaw Chopin, and led to heightened security alerts in Poland's eastern provinces. This military action represents Poland's first direct response to Russia's aggression amid escalating regional tensions.
Indeed, NATO's relationship with Russia has reached a historic low. Once a more cooperative partnership, ties between the North Atlantic Treaty Organization and Moscow have deteriorated sharply, today resembling the tense standoff of the Cold War. NATO leaders view Russia as a direct security threat, but repeated warnings and condemnations from the Alliance have so far had little effect on the Kremlin.
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.