Nato will unveil its most significant shift in policy since the Cold War to counter the threat posed by Russia, the alliance’s secretary-general Jens Stoltenberg said Monday ahead of a summit taking place in Madrid this week.

At a press conference in Brussels, Stoltenberg said the summit would be “transformative” and would see “many important decisions” taken, including on a “new strategic concept for a new security reality” in the wake of Russia’s invasion of Ukraine.

The concept represents a “fundamental shift in Nato’s deterrence and defense” as well as guaranteeing “support to Ukraine now and for the future,” he said.

“Our new concept will guide us in an era of strategic competition,” Stoltenberg continued, adding that the alliance’s conceptual shift will “make clear that allies consider Russia as the most significant and direct threat to our security.”