"I've seen some reports that our army is not doing great and that if there was a war it wouldn't take that much time for Russia to take over some of our land," said a resident of Warsaw.

In recent months, thousands of Poles here in Warsaw have signed up for military training. The government aims to create an Israel-style reserve force numbering some 500,000. 

"I've recently been participating in a public debate on what happens and what I would do as a citizen, whether I would run away or I would stay and fight, and I have to admit that I don't know what I'm going to do," said another resident of Poland's capital city.

In September, 30,000 Polish and NATO troops took part in one of the largest military drills in the country's history.

The exercise unfolded less than 60 miles from the Suwałki Gap, a narrow stretch connecting the Baltic states to the rest of NATO. 

Experts say if Russia ever attacks, this could be one of its first targets.

"The importance and strategic significance of the Suwalki Corridor is undeniable," said Gitanas Nausėda, President of Lithuania.

Last month, a new highway opened linking the Baltic states to Poland. 

It cuts right through the Suwałki Gap, between Belarus and Russia's Kaliningrad enclave.

"It is a very important artery not only for the movement of goods and people, but also for military mobility," noted Nausėda.

With Russian drones testing NATO's borders and tensions rising across Europe, one question looms large: not if the alliance is ready, but how soon it may have to prove it.