Final answer:
King George III ignored the Olive Branch Petition and declared the colonies in rebellion, which led the Continental Congress to create an army and prepare for war in anticipation of further hostilities.
Step-by-step explanation:
King George III reacted to the Olive Branch Petition by ignoring it and declaring that the colonies were in open and avowed rebellion. The petition was an attempt by the Second Continental Congress to avoid a full-blown war by showing loyalty to the Crown and seeking a peaceful resolution to the grievances of the American colonies. In response to the petition, King George III refused to initiate negotiations or provide a formal apology; instead, he increased hostilities and made preparations for military action against the colonies.
The Continental Congress created an army and began preparing for war before receiving a response to the Olive Branch Petition because it became evident that the King and Parliament were not going to offer a conciliatory response. With the Prohibitory Act, the declaration of Massachusetts Bay in rebellion, and the British actions at Lexington and Concord, Congress felt compelled to prepare for the worst. Hence, they raised funds, formed the Continental Army, and appointed George Washington as commander-in-chief.