The 1618 to 1648 Thirty Years' War was fought primarily in Central Europe. It was one of the most devastating European conflicts.The actual war began with the revolution of the estates in the lands of the Czech Crown.

Tragic anniversary - execution in Praha 21st June 1621

In these days Czechia is remembering very sad and at the same time extremely important event
of our history which happened 400 years ago. It is the Old Town Square execution which happened on 21th June 1621 in Praha when 27 Bohemian leaders (noblemen, knights and burghers) who took part in the protestant uprising were beheaded. This Bohemain revolt began after the Prague Defenestration in 1618 and subsequent Protestant uprising of the Bohemian estates against the Catholic Habsburgs. 
But on November 8, 1620, the Battle of White Mountain took place, resulting in the fatal defeat of the Protestant resistance. Habsburgs took their revenge and executed some of the key leaders of the uprising, although with some others the punishment was reduced and some were pardoned.
Dozens of carpenters and their apprentices had laboured for days on Prague's Old Town Square, their mission: to complete a stage and gallows planned for a most grisly event - the execution of 27 noblemen who had played key roles in the Protestant revolt.

More details you can read here

https://en.wikipedia.org/wiki/Old_Town_Square_execution

The place of execution and the sad end of the estate uprising are reminiscent of Cobblestones, which mark the area where the execution site stood.

Consequences:

Execution was only one of the consequences of the uprising, which turned out to be unsuccessful. Other consequences were the hereditary possession of the Czech royal crown in the hands of the Habsburgs, which meant another almost 300 years of their domination. Another major consequence was the subsequent re-Catholicization, which meant a great wave of emigrants (which was the majority of the Czech intelligentsia) and the conversion of those who remained. The German language was on an equal footing with the Czech language.

If you are interested in this chapter of European history you can read more detailed informations here
https://veritas.evangnet.cz/en/executions-1621
The macabre sight of execution was to deter enemies of Habsburgs  but the executed men were soon considered as Protestant martyrs and their death started to be a subject of literal works.

         Thanks for reading

                                          Margaret