Seldom before has a NATO summit been so blatantly militaristic. Tanks were lined up at the site of the conference in Wales on Friday, and a scale-model combat aircraft graced the entrance to the meeting site. This set dressing, an expression of the UK's carefree approach to all things military, also sent another message: NATO has returned to its core mission as a defensive alliance.

The change has come in response to external pressure, almost with a certain inevitability. And for so many NATO members, the old terms are now back in play: deterrence and containment, the language of the Cold War. But what other choice is there for a military alliance when a new/old enemy is using military power politics and changing borders in Eastern Europe by force?

Christian Trippe is a special correspondent for DW

NATO has responded with a readiness plan to reassure its members, especially those in the east. For the so-called Putin doctrine has set off alarm bells in Tallinn and Riga. Russia has claimed the right to intervene outside its borders in order to protect Russian-speaking minorities. In Crimea earlier this year, the Russian president demonstrated how something like this is enforced - and its outcome. Estonia and Latvia have sizeable Russian minorities, and Moscow will likely not find it difficult to find a reason to "protect" them.

But NATO's newly approved rapid response force is not a solution for the security problems in the east. At most, it can offer protection against those "little green men," soldiers in unmarked uniforms who have infiltrated the area. Those in control at NATO know only too well that the Baltic states would be vulnerable in a conventional war. And so, the alliance needs to revamp its strategy.

NATO's current strategic calculus is based on a simple premise: that Vladimir Putin will respect the red line that has been drawn around the alliance's borders. In other words, NATO is relying on the belief that the leadership in Moscow will be intimidated by the promise of mutual assistance and treaty obligations outlined in Article 5 of the NATO treaty.

But what if Putin decides - whether it be with an "unorthodox" intervention, or military operation by air and on the ground - to "test" the Article 5 pledge in the Baltic states? Will NATO troops die for Tallinn? Will there be nuclear retaliation for Riga? These questions are not academic, and not limited to pacifist groups. They are being discussed by NATO - but the new task force is not providing any answers.

And Ukraine? NATO has not been stingy, offering loud assurances of solidarity and symbolic pledges of aid for Kyiv. And yet the country has been left to itself in its conflict with Russia. Real assistance - that's something that the alliance is unable to offer. Ukraine lies on the other side of the red line, and Putin is well aware of this fact.