This year marks the 70th anniversary of NATO, which its 29 members will commemorate on 3 and 4 December in London. To be clear: this will not be a regular NATO ‘Summit’. The gathering has a less formal status and will not be concluded with a common statement on how to move forward. Rumour has it that changing the name to a NATO’s ‘Leaders Meeting’ was inspired by President Trump’s capricious behaviour during past summits. This development is indicative of a larger problem: disunity within the Alliance. NATO is the most important security organisation of our time, but is it aware of its most pressing threat?