Final answer:
Andrew Jackson first gained national fame as a military hero during the War of 1812, specifically through his victory at the Battle of New Orleans.
Step-by-step explanation:
Andrew Jackson first gained national fame as a military hero during the War of 1812. His forces achieved a significant victory at the Battle of New Orleans in 1815, which defended the city and the Mississippi River Valley from British invasion. This success catapulted Jackson to national prominence as a war hero and later played a significant role in his rise to the presidency.
Learn more about Andrew Jackson's rise to national fame