Why defeating Britain required a workable invasion

Could Germany have forced Britain out of the war without attacking the Soviet Union, or would it have run out of oil first?

A successful invasion is judged necessary, and Germany lacked a workable way to reach Britain. When German oil would have run out remains unresolved.

In this assessment, Germany could not force Britain out of the war without solving the invasion problem. Defeating continental opponents required a large army, while reaching Britain required a navy capable of getting that army across the Channel. Napoleon's invasion plans are judged more coherent than Sea Lion, although still poor. No timetable for German oil exhaustion is established.