Final answer:
Churchill believed an invasion of British soil was not likely because Germany did not have air superiority after the RAF won the Battle of Britain.
Step-by-step explanation:
Winston Churchill believed that an invasion of British soil was not likely to occur in the near future primarily because the enemy, Nazi Germany, did not have air superiority over Britain. During what was known as the Battle of Britain, the German Luftwaffe and the British Royal Air Force (RAF) fought for control of the skies. Despite having fewer planes, the British pilots, assisted by the country's development of radar and inspired by Churchill's leadership, won the battle, which saved Britain from invasion. This victory was so critical that Churchill famously remarked, “Never before in the field of human conflict has so much been owed by so many to so few,” underscoring the importance of the RAF's victory in protecting the UK from a ground invasion.