The British decision to focus their strategy on the Southern colonies was largely based on the perception, partly a valid one, that there were more loyalists in the South than elsewhere in the colonies. The British reasoned that if they could encourage and energize the Southern colonists, these people would aid them in the war effort. Then, the campaign to overturn the rebellion would spread to the other colonies north of the Mason-Dixon line. In theory this, to a degree, made sense, but various missteps by the British and a basic misunderstanding of the methods by which the various rebel armies were fighting led eventually to the final failure of their efforts to stop the rebellion, culminating in Yorktown in October 1781.
In general the progress of the war, since its beginning, had principally been a movement from north to south. The fighting, of course, was initiated in New England in 1775. When the British were forced to evacuate Boston the following year, they then made New York the focus of their efforts, winning all the battles in the New York area and forcing Washington to retreat south through New Jersey but never actually destroying his army. His surprise victories over them at Trenton and Princeton demoralized the British and made other European leaders realize for the first time that the rebellion could actually succeed. In 1777, Howe landed in the Chesapeake Bay at Head of Elk, Maryland (today Elkton), quickly advanced north, defeated Washington again at Brandywine and then marched into Philadelphia. But the following year, he abandoned Philadelphia. In the meantime, the devastating defeat of Burgoyne's army at Saratoga showed that the British, despite seeming to be able to take American cities whenever they wished, were farther from quashing the rebellion than they had been at any time since the start of the fighting. With the news that the French had formed an alliance with the rebel government, the British began to realize they were in a quagmire, unable to make progress in spite of numerous victories in the field and the near disintegration of Washington's army in the winter of 1777–1778 at Valley Forge.
Hence the Southern strategy was developed, which was both something new and, as stated, also a kind of continuation of the general southward progress of the war. The British seemed to believe that if they were not able to end the rebellion in one region, they could move to another area and try again. But the manner in which this phase was conducted seemed to combine, in an even worse form, all the errors the British had previously made through the conflict to this point. For one thing, the brutal tactics they employed in the South had the effect of turning much of even the loyal population against them. Various officers, in particular General Tarleton, carried out actions that were seen as indiscriminately destructive. He burned property and killed farm animals throughout the Carolinas.
This was the key factor as to why the British "invasion" of the South backfired, for even if a majority of Southerners were loyalists and wished to remain under the Crown, they still did not want the war or its violence brought to their country. The appearance of the British became a catalyst for a savage internecine warfare amongst the Americans themselves. The Americans who were against the British were well organized. A small army of rural people who lived largely in the borderlands between North and South Carolina destroyed a British force at the Battle of King's Mountain in 1780. At the battle of Cowpens, Daniel Morgan's forces, using creative and unorthodox tactics, similarly defeated the British. Nathaniel Greene's army, though it did not actually win a single battle, fought the British over and over again, constantly losing but surviving to fight another day while exhausting the British. It became a classic war of attrition in which the British were unable to extend their supply lines. The British were eventually trapped at Yorktown between Washington's and Rochambeau's armies and the French fleet under De Grasse, which had arrived in a miracle of timing. This was the final straw for the British Parliament, who realized that the war would go on and on indefinitely without resolution, even if another army was sent across the Atlantic to replace Cornwallis's defeated forces. The Tory government fell, and the Whigs, who had been sympathetic to the Americans and against the war from the beginning, voted to begin peace negotiations.