Why an Axis seizure of Gibraltar would not sever Britain

What if German forces helped Franco capture Gibraltar during the Second World War?

The fortress would be difficult to subdue and its loss would hurt Mediterranean operations, but Britain would retain its Atlantic supply routes and could exert major pressure on Spain.

Gibraltar's defenses extended into the rock, so capturing the visible surface positions would not instantly end resistance. Britain could reinforce or evacuate according to wider Royal Navy priorities, while Spain would expose its own shipping and economy to British pressure. The premise also depends on a different Spanish political outcome, which would have affected earlier British support for the Republican side. Most importantly, Gibraltar did not control the Atlantic routes from Canada and the United States, so its loss would complicate Mediterranean strategy rather than isolate Britain from overseas supply.