 Following another unsuccessful invasion of Geneva by Savoy forces in October 1535, which ended in a Savoy defeat at Gingins, the Grand Council decided on February 3, 1536 on the destruction of all castles around Geneva in order not to allow any princes another pretext for invading their city.On May 21, 1536, the Genevans declared themselves Protestant by taking a public oath of allegiance to the Lutheran faith where all residents took part, and proclaimed their city a republic.This move was in the making for a long time, but was delayed for fears of Savoy invasion.