The opposing sides in the American Revolutionary War had various advantages and disadvantages. The colonists lacked sufficient funds, soldiers, and training, but used effective guerrilla warfare tactics. The British had stronger arms and equipment and hired German mercenaries, but the war was unpopular in Britain. A series of key battles then shifted the war in favor of the colonists. Washington's surprise attack on Hessian troops in Trenton was a boost, as was the colonists' holding out at Valley Forge. The decisive victory over British forces at Saratoga convinced the French to formally support the colonists. Finally, the British general Cornwallis surrendered his forces at Yorktown, leading Britain to recognize American independence in the Treaty of