High Quality Content by WIKIPEDIA articles! The military history of Gibraltar during World War II exemplifies Gibraltar`s position as a British fortress since the early 18th century and as a vital factor in British military strategy, both as a foothold on the continent of Europe, and as a bastion of British sea power. During World War II, Gibraltar served a vital role in both the Atlantic Theatre and the Mediterranean Theatre, controlling virtually all naval traffic into and out of the Mediterranean Sea from the Atlantic Ocean.