Why was the Declaration of Independence written?

The Declaration of Independence was written for two reasons. First, as the name suggests, it was intended to declare the independence of Britain's North American colonies from their mother country. The colonies had been at war with Britain since April of 1775, and after much debate, the advocates for independence in the Second Continental Congress at Philadelphia had won out. The Declaration was thus a statement of the intent of these delegates, and the assemblies that chose them, to set out on their own as an independent nation. It transformed the Revolutionary War from a struggle over the rights of Englishmen to a war to free the colonies from British rule. The Declaration, however, had another major purpose. It was to state the ideological principles and the perceived British abuses that motivated the colonists in the first place. In the first part of the document, Thomas Jefferson outlines the purpose of government, which, he says, echoing John Locke, is to protect the unalienable rights of man. He goes on to say that, when governments abuse these rights, people have the right to "alter or abolish" the offending government. This, the document explains, is why the colonists took up arms, and why they are declaring independence. The document goes on to list a series of "injuries and usurpations" suffered by the colonists that, the signers asserted, justified their actions. For these reasons, the Declaration was written, signed, and promulgated throughout the colonies.