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BATTLE // September 19, 1618

Siege of Pilsen

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Overview

The Siege of Pilsen, 19 September to 21 November 1618, was the first significant action of the Thirty Years' War. Following the Bohemian Revolt, a Bohemian army under Ernst von Mansfeld captured Plzeň.

Overview adapted from Wikipedia, licensed under CC BY-SA 4.0.

Significance

The Siege of Pilsen, lasting from 19 September to 21 November 1618, was the first significant military action of the Thirty Years' War. Following the Bohemian Revolt — the proximate cause of the broader conflict — a Bohemian army under Ernst von Mansfeld captured Plzeň from a substantially smaller Habsburg garrison. The disparity in recorded force sizes, 20,000 Bohemian troops against 4,000 Habsburg defenders, underscores the weight brought to bear on the city. Habsburg casualties of 2,500 against Bohemian losses of 1,100 reflect the cost of the defense. As the opening operational episode of a war that would consume Central Europe for three decades, the fall of Plzeň established early Bohemian momentum in the revolt against Habsburg authority and marked the transition from the political crisis of the Defenestration of Prague into open armed conflict.

Forces & casualties

Troop strength

  • Bohemia20,000
    medium
  • Habsburg Monarchy4,000
    medium

Bohemia fielded a 5.0 : 1 numerical advantage

Casualties

  • Bohemia1,100
    medium6% loss rate
  • Habsburg Monarchy2,500
    medium63% loss rate

Commanders (2)

Habsburg Monarchy

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Last verified July 2026
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