Final answer:
Major General Robert Ross was mortally wounded by American snipers during the British march to Baltimore and later died en route back to the ships. His death led to the ultimate withdrawal of British forces from the assault on Baltimore.
Step-by-step explanation:
Cause of Major General Robert Ross's Death
The cause of Major General Robert Ross's death was a gunshot wound inflicted by American snipers. During the march to Baltimore, Ross led 5,000 British troops and was targeted by the snipers, who were deployed to delay the British forces and allow more time for the defenders of Baltimore to fortify their positions. Mortally wounded, Ross was carried back to the ships but succumbed to his injuries along the way. The British advancement was ultimately stopped due to stiff resistance from the American defenders, who utilized artillery and defensive works effectively.
Following the failure of both land and naval attacks and the death of their army commander, the British withdrew from the assault on Baltimore and set sail for New Orleans.