The siege of Deventer was a siege of the city of Deventer by States troops under George van Lalaing, count of Rennenberg, from 3 August to 19 November 1578 during the Eighty Years' War. It was besieged in an attempt by the States-General of the Netherlands to better protect the regions of Holland and Utrecht from Spanish plundering. Since 1572 the city had been held by the German Polweiler-regiment for the Spanish Empire on behalf of Don John of Austria. After Lalaing had put into practice a number of pieces of strategic advice from Johan van den Kornput, the city was prepared to negotiate a surrender and on 19 November 1578 handed itself over to States troops.
| Siege of Deventer (1578) | |||||||||
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| Part of the Eighty Years' War | |||||||||
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| Belligerents | |||||||||
 States-General of the Netherlands |  German garrison under Spanish command | ||||||||
| Commanders and leaders | |||||||||
| Graaf van Rennenberg Diederik Sonoy | Augustyn Ryck Haurincourt | ||||||||
| Strength | |||||||||
| Army of Rennenberg: 10 detachments (around 1,300) French army: 1,000 | 900 | ||||||||
| Casualties and losses | |||||||||
| Unknown | 300 | ||||||||