Final answer:
Historian D. Nan, who reviews English military records, is using an outside perspective to analyze the American Revolution, which aligns with the approach of the imperial school of historians.
Step-by-step explanation:
Historian D. Nan is using an outside perspective to analyze the American Revolution by reviewing English military records from the period. This approach provides a viewpoint from the British side of the conflict which is a way of understanding the American Revolution within the larger context of the British Empire, aligning with the perspective of the imperial school of historians.
Historians who adopt an outside perspective on the American Revolution typically examine sources or viewpoints that originate from outside the American colonial context. These historians often challenge nationalistic interpretations and seek to understand the conflict as part of wider imperial dynamics. They might argue, for instance, that issues of constitutional conflict and differing views on governance created an irreconcilable rift between the colonies and Great Britain, as suggested by the works of George Beer, Charles Andrews, and Lawrence Gipson.