20 Zlotys The Polish Thermopylae – Węgrów

Węgrów, January 1863. Three days into the January Uprising against Russian imperial rule, a force of roughly 600 poorly armed Polish insurgents held off a Russian column of several thousand troops for the better part of a day before being overwhelmed. The engagement became known almost immediately as "the Polish Thermopylae" — a designation that stuck precisely because the outcome was the same: tactical defeat, symbolic immortality.

The January Uprising itself lasted eighteen months and ended in mass executions, Siberian deportations, and the abolition of the Kingdom of Poland's remaining autonomous institutions.