As the world marks the one-year anniversary since Russia's all-out invasion of Ukraine, Warsaw has reinforced its border with Russia and Belarus.
"This is part of our defence and deterrence strategy," Defence Minister Mariusz Blaszczak tweeted on Thursday.
He said the first barrier was set up on the border with the Russian exclave of Kaliningrad, and posted an image of the anti-tank barriers - angled metal beams that prevent the entry of armoured vehicles.
Poland has a 200-kilometre border with the Kaliningrad region.
Warsaw also plans to set up anti-tank barriers on its border with Belarus, which is some 418 kilometres in length, as leader Alexander Lukashenko is an ally of Russian President Vladimir Putin and Russian forces have launched attacks into Ukraine from Belarus.
So far, the smaller country has not actively intervened in the Kremlin's war on Ukraine.
Poland's latest reinforcements come after Warsaw adopted measures along the border last year, building a 5.5-metre fence on sections of the border with Belarus.
The move came after Minsk deliberately encouraged migrants to enter the EU through Poland in what was seen as an attempt to destabilize the bloc, amid a spat over sanctions imposed due to a disputed election and crackdown.
