dreamcompiler wrote: “Russia's trains had to stop at the Ukrainian border because of the gauge difference.”

There is no gauge difference between Russia and Ukraine.

In fact, even some (small) parts of Polish railways use Russian gauge - remnant of the times when Soviet raw materials were delivered in bulk to Polish metallurgic plants.

Side note: This gauge difference worked in Ukraine's favor in one respect. Russia's military logistics infrastructure is heavily train-based, but Russia's trains had to stop at the Ukrainian border because of the gauge difference. This meant they had to switch to trucks which are old and unreliable and they got bogged down in mud, which meant they had to stick to roads where they were easy for the Ukrainians to attack. And those transshipment points where the Russians had to unload all their cargo from trains and reload it onto trucks also became fat juicy targets.

Yet another example where Russia didn't think carefully enough before invading.

Ukranian and Russian railway gauge are the same, 1520mm.

It is EU that is different with 1435mm.

I read an article early in the war that specifically stated the opposite, but apparently it was wrong and now of course I can't find it. You're correct.

Why in the world are train crossings from Poland to Germany not electrified yet??