# Crusade against the Prussians fails (1166)

URL: https://poland-history.com/timeline/1166-crusade-against-the-prussians-fails
Location: Prussia
Categories: battle

Duke Henry of Sandomierz was killed during an expedition against the pagan Prussians, whose raids continued to threaten Masovia. Within the broader Fragmentation period: After 1138 Poland split into duchies ruled by rival Piast princes. Mongol invasions, German settlement, the growth of towns and the arrival of the Teutonic Knights reshaped the land before it was reunited. At this point in the timeline (1166), the governing authority was Bolesław IV the Curly (High Duke of Poland). Senior duke who submitted to Frederick Barbarossa in 1157 but preserved the Piast realm's integrity. Crusade against the Prussians fails mattered because it changed the military or territorial balance and influenced the political choices that followed. The event is placed here so readers can follow it alongside changes in government, warfare, society, religion and culture across Polish history.

## Why it matters
Crusade against the Prussians fails mattered because it changed the military or territorial balance and influenced the political choices that followed.

Ruler at the time: [Bolesław IV the Curly](https://poland-history.com/rulers/boleslaw-iv-the-curly)

## Sources
- [Wikipedia — Henry of Sandomierz](https://en.wikipedia.org/wiki/Henry_of_Sandomierz)
- [Encyclopaedia Britannica topic lookup — Crusade against the Prussians fails](https://www.britannica.com/search?query=Crusade+against+the+Prussians+fails)
- [Wikipedia — History of Poland during the Piast dynasty (period overview)](https://en.wikipedia.org/wiki/History_of_Poland_during_the_Piast_dynasty#Fragmentation_of_the_realm_(1138%E2%80%931320))