Poland has invoked article 4 of the NATO treaty. This is only the fourth time the article has been invoked. Ivo Doalder:
Article 4 provides for consultations of the NATO members “whenever, in opinion of any of them, the territorial integrity, political independence or security of any of the Parties is threatened." Such consultations are rare—this would be only the fourth time they have happened. . .
The decision by Poland to invoke Article 4 indicates that Warsaw—along with the three Baltic Allies—is concerned that developments in neighboring Ukraine poses a threat to its security. This is understandable, given the fact that Russian President Putin not only sought (and received) authorization to use its armed forces throughout Ukraine, but has justified this move in terms of the need to protect “Russian-speaking” people—many of which reside in other parts of eastern Europe.
Doalder recommends beefing up NATO air and ground forces in Poland and the Baltics. Exactly how strong or weak the Russian armed forces are is seemingly a contentious question, but the core of NATO's strength is the US, and to a much lesser extent Germany. And the US is pretty far away.