In all senses of a defensive army, that is exactly what NATO is.
The only countries not in NATO in Europe, that are not landlocked or geographically irrelevant (Ireland), are Sweden and Finland.
Both of these traditionally consider themselves non-aligned. However, every year, especially Sweden which is the more important of the two due to its Baltic territory, moves closer to NATO. Despite their non-aligned status, they both signed a host nation agreement to allow NATO to use their territory and they just recently entered into a cooperation agreement with each other in event of war from an external threat. This is directly as a result of Russian actions in the area.