The Alteratie (Eng: Alteration) is the name given to the change of power in Amsterdam on May 26, 1578, when the Catholic city government was deposed in favor of a Protestant one. The coup should be seen in the context of the greater Dutch Revolt that was breaking out in this time. Trade interests played an important role, because Amsterdam was becoming isolated as surrounding cities and towns joined the revolt, and other cities were threatening to take over its trade. No one was injured or killed during the coup. On May 29, a new city council was formed, consisting of 30 Calvinists and 10 Catholics. Already after a few months, plans were presented to expand the city and the harbor on the eastern side (Lastage), and to construct new defensive fortifications (Oude Schans).