One characteristic of the Committees of Correspondence was that they were formed in opposition to British taxation and other policies enacted during the imperial crisis that led to the outbreak of the American Revolution. The first of these committees was formed in Boston, even before the Stamp Act was passed, in response to the Sugar Act and other revisions to colonial policy by Parliament. The second characteristic of these committees was that they spread information and news between the colonies in the midst of these crises. The effect of these committees was to foster a sense of unity in the colonies. The committees reinforced the idea that the struggle of the Massachusetts colonists was the struggle of all the colonies, and that the colonies should appear as a united front in the boycotts they used to protest what they saw as oppression. Many of the local committees became revolutionary committees of safety after 1774.