Consequently the blockade was useless to Great Britain; and so, in the first six months of the war, the Admiralty fell back upon the milder system of declaring certain articles contraband of war and seizing ships that were suspected of carrying them to Germany.
A geographical accident had apparently largely destroyed the usefulness of the British fleet and had guaranteed Germany an unending supply of those foodstuffs without which she could not maintain her resistance for any extended period.

Was Great Britain called upon to accept this situation and to deny herself the use of the blockade in this, the greatest struggle in her history?
Unless the British fleet could stop cargoes which were really destined to Germany but which were bound for neutral ports, Great Britain could not win the war; if the British fleet could intercept such cargoes, then the chances strongly favoured victory.

The experts of the Foreign Office searched the history of blockades and found something which resembled a precedent in the practices of the American Navy during the Civil War.

In that conflict Nassau, in the Bahamas, and Matamoros, in Mexico, played a part not unlike that played by Rotterdam and Copenhagen in the recent struggle.
These were both neutral ports and therefore outside the jurisdiction of the United States, just as Rotterdam and Copenhagen were outside the jurisdiction of Great Britain.

They were the ports of powers with which the United States was at peace, and therefore they could not be blockaded, just as Amsterdam and Copenhagen were ports of powers with which Great Britain was now at peace.
Trade from Great Britain to the Bahamas and Mexico was ostensibly trade from one neutral port to another neutral port in the same sense as was trade from the United States to Holland and Denmark.