Because of its geographical location, the Shetland Islands played a significant role during both world wars. The British Royal Navy used the nearby Orkney Islands as their main naval base, so a German invasion of the Shetlands could pose an immediate threat to their fleet. Defences like coastal batteries, airfields and roadblocks were built to protect the islands. The Shetlands were also important during the Battle of the Atlantic. The many radar stations scanned the skies and seas to support the navy and airforce while patrolling the surrounding waters.