Final answer:
Polish nobleman and military commander Casimir Pulaski died during the Siege of Savannah in the Revolutionary War, contributing significantly to the American military with his cavalry expertise.
Step-by-step explanation:
The foreign patriot who died during the Siege of Savannah was Casimir Pulaski, a Polish nobleman and military commander who has been known as "The Father of American Cavalry". Pulaski was mortally wounded by grape shot on October 9, 1779, while leading a cavalry charge against British fortifications in Savannah, Georgia. His death is a significant event in the history of the Revolutionary War because Pulaski brought valuable cavalry expertise to the Continental Army and contributed to the development of American military tactics.