NATO plans to mobilize 90,000 soldiers for a manoeuvre aimed at deterring Russian aggression, in the biggest exercise staged by the alliance since the end of the Cold War. According to information obtained by dpa on Thursday, the scenario for the Steadfast Defender exercise due to start in February is a Russian attack on allied territory that triggers Article 5 of the NATO treaty that enshrines the promise of collective defence. Article 5 has been invoked only once, in the wake of the September 11, 2001 attacks by al-Qaeda on the United States. The largest post-Cold War NATO exercises were sta…