Final answer:
The policy that led to Britain's seizing of American sailors and forcing them to serve in the British Royal Navy was impressment.
Step-by-step explanation:
The policy that led to Britain's seizing of over 6,200 American sailors and forcing them to serve in the British Royal Navy was impressment. This practice involved the kidnapping of American sailors and their forced service in the British Navy, which was a major grievance of the United States during the early 19th century.
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