Stopping a major combined arms invasion from an easterly neighbor is the focus of all of Germany's big training exercises to this day. Instead of whatever the Heer says through its public affairs officers, look at what is actually being practiced and paid for with the Euros in the defense budget. It's not counterinsurgency, it's not disaster relief, it's training out of Wildflecken focused on stopping a theoretical invader from penetrating the Fulda Gap with tanks.

The German military in 2017 could probably not stop an invasion by Canada. NATO on the other hand, most certainly exists to deter Russian aggression.