Final answer:
The British lost the key battle in the South due to General Nathanael Greene's strategic avoidance of direct confrontations, leading to decisive battles like Cowpens and significant British losses at Guilford Courthouse, resulting in their eventual surrender at Yorktown.
Step-by-step explanation:
The reason the British lost the key battle in the South was multifaceted. One of the primary reasons was the strategic leadership of George Washington and General Nathanael Greene, who leveraged the French alliance to their advantage. The British initially had successes in the South, thanks to their southern strategy, capturing Savannah and gaining the support of Loyalists, enslaved people, and Native American allies. However, their fortunes turned when General Greene's tactic of avoiding full-scale engagement while wearing down isolated British units succeeded. This strategy culminated in decisive American victories such as the Battle of Cowpens and led to substantial British losses at the Battle of Guilford Courthouse. Eventually, the British forces, led by General Cornwallis, retreated to Yorktown where they were besieged and ultimately forced to surrender, thus ending major British military operations in the American Revolutionary War.