The Article 5 guarantee has always been a political instrument as much as a military one. Remove the political will behind it and the military architecture starts to look very different.
The eastern flank — Poland, the Baltic states, Romania, and now Finland and Sweden — has been the most serious part of NATO since 2014. These countries have spent, planned, and positioned as if the threat were real, because for them it is. The presence of U.S. forces, however limited in number, has served as a tripwire: a signal that any Russian incursion into NATO territory would immediately involve American casualties and therefore American response.
Strip that assumption and what remains is a European military architecture that is better than it was five years ago, but structurally incomplete. The Baltic states in particular are exposed. They are geographically isolated, have limited strategic depth, and depend on rapid reinforcement through corridors — particularly the Suwalki Gap — that would be contested from day one of any conflict.
Poland is the exception in a meaningful way. Warsaw has been building toward genuine independent capability: large ground forces, significant procurement of U.S. and Korean equipment, and a political culture that takes the threat seriously at every level of government. If there is a European anchor on the eastern flank, it is Poland.
The broader question is whether a European deterrent — even a well-funded one — can substitute for extended U.S. deterrence in the near term. The honest answer is no. Not because European militaries are incapable, but because deterrence is as much about credibility and signaling as it is about hardware, and that credibility takes time to establish.
The flank is more defensible than it was. It is not yet self-sufficient. The gap between those two things is where the risk lives.