Patriot missiles ring the airport in the Polish border city of Rzeszów, and US troops have taken over the Holiday Inn opposite the terminal. On its runway, once the preserve of budget carriers, private jets are lined up beside cargo planes crammed with weapons.

The bristling circle of military protection, set up hastily in early spring as the historic town became the world’s gateway to the war in Ukraine, is both a shield and a constant reminder of the conflict on its doorstep.

When a Russian-made missile slammed into a farm and killed two men in the village of Przewodów, about 100 miles away, many people wondered if it was enough.

“After this incident in Przewodów, I and many of our citizens had a moment of great fear,” said Rzeszów mayor Konrad Fijołek, sitting in his busy town hall office. “Is this the beginning of something worse? Was it a Russian missile or not? And why didn’t our systems catch it?”

This war has changed the world, but perhaps nowhere outside Ukraine has the transformation forged by Moscow’s guns, tanks and missiles been as immediate and far-reaching as along Poland’s border.

Here, the day of the invasion, 24 February, is etched into history. People use the date as shorthand for Vladimir Putin’s annexation project, the way Americans refer to 9/11.

Ukraine has named Rzeszów “saviour city”,…