“Russia’s full-scale invasion of Ukraine has prompted the North Atlantic Treaty Organisation to restore its own military capabilities to Cold War-era levels, as well as to reconsider its approach to deterrence on its eastern borders.
Source: The New York Times
Details: As The New York Times wrote, NATO is rapidly moving from what the military calls deterrence by retaliation to deterrence by denial.
Previously, in the event of a Russian invasion, member states had to hold out until allied forces, mainly the US, came to their aid and retaliated to push the Russians back.
But after the Russian atrocities in areas it occupied in Ukraine, Poland and the Baltic countries no longer want to risk any period of Russian occupation. As in the first days of the Ukrainian invasion, Russian troops took land larger than some Baltic nations.
“Deterrence by denial” means, on the contrary, the permanent location of allied troops near the border with the Russian Federation, more integration of American and allied war plans, more military spending and more detailed requirements for allies to have specific kinds of forces and equipment to fight, if necessary, in pre-assigned places.”
https://www.yahoo.com/news/nato-no-longer-allows-temporary-161118238.html