Final answer:
The British army launched a southern offensive in 1778 during the Revolutionary War because they expected more support from Loyalists in the southern colonies. By capturing Savannah and regaining control in Georgia, the British gained political control and formed Loyalist regiments.
Step-by-step explanation:
The British army likely decided to launch a southern offensive in 1778 during the Revolutionary War because they anticipated more support from Loyalists in the southern colonies. This was part of a revised strategy to break the stalemate in the North and gain control over the southern colonies. By capturing Savannah, the capital of Georgia, and regaining political control in Georgia, the British were able to force inhabitants to swear allegiance to the king and form Loyalist regiments.