In July 1914, the Royal Navy initiated the observational and distant blockades. The North Sea was filled with ‘observational’ vessels that patrolled its waters looking for enemy ships, submarines and contraband, and stopping and searching shipping. Contraband meant any foods or raw materials destined for Germany. Within weeks, surveillance was extended to include the Dover Straits and northern France; north of Scotland and Norway (the distant blockade). On 3 November 1914, the North Sea was declared a ‘military area’ and minefields were laid. Neutral vessels entered at their own risk and were given a naval escort. The area between Jutland and the Netherlands was completely blocked by the British Royal Navy, preventing German access to the Atlantic. The blockades were successful and remained until 1919. The food embargo was controversial at the time, as it was thought to contravene international law.