Final answer:
John C. Calhoun from South Carolina was the prominent leader of the War Hawks advocating for war with Britain.
Step-by-step explanation:
The leader of the War Hawks for the southern states who advocated going to war with Britain in 1812 was John C. Calhoun from South Carolina. Along with Henry Clay from Kentucky, Calhoun played a pivotal role in stoking the desire for war as a response to British provocations, including the seizure of American ships and the impressment of sailors, as well as backing Native American resistance against the United States. The determination of men like Calhoun and Clay, who would not stand for British insults to American honor, contributed significantly to the U.S. Congress's narrow decision to declare war on Britain in June 1812.