This article presents the role of the civic guard in the defence of Gdańsk during the conflict with Polish King Stefan Batory in 1576–1577, as well as its organisation and the regulations defining military duties and restrictions for breaking them. Apart from mercenaries, the citizen militia was the main defensive force. The issue of organising the defence of cities by their citizens in the Old Polish period has not been particularly appreciated in Polish historiography, mainly because of the weakness of Polish cities. Gdańsk’s war with Stefan Batory was exceptional and is quite well documented. Historical sources show the tremendous effort of the inhabitants, who first built a system of fortifications around the city and then proceeded to defend it. After the defeat of the Gdańsk army at the Battle of Lubieszów, they were the main force of resistance for several weeks. As a result of their sacrifice, Gdańsk was not captured and did not lose its unique position in the maritime policy of the Polish state.