Yet the convoy, as used in previous wars, differed materially from any application of the idea which could possibly be made to the present contest. This scheme of sailing vessels in groups, and escorting them by warships, is almost as old as naval warfare itself. As early as the thirteenth century, the merchants of the Hanseatic League were compelled to sail their ships in convoy as a protection against the pirates who were then constantly lurking in the Baltic Sea. The Government of Venice used this same device to protect its enormous commerce. In the fifteenth century the large trade in wool and wine which existed between England and the Moorish ports of Spain was safeguarded by convoys, and in the sixteenth century Spain herself regularly depended upon massing her ships to defend her commerce with the West Indies against the piratical attacks of English and French adventurers. The escorts provided for these "flotas" really laid the foundation of the mighty Spanish fleet which threatened England's existence for more than a hundred years. By the time of Queen Elizabeth the convoy had thus become the all-prevailing method of safeguarding merchant shipping, but it was in the Napoleonic wars that it had reached its greatest usefulness. The convoys of that period were managed with some military precision; there were carefully stipulated methods of collecting the ships, of meeting the cruiser escorts at the appointed rendezvous, and of dispersing them when the danger zone was passed; and naval officers were systematically put in charge. The convoys of this period were very large; from 200 to 300 ships were not an unusual gathering, and sometimes 500 or more would get together at certain important places, such as the entrance to the Baltic. But these ships, of course, were very small compared with those of the present time. It was only necessary to supply such aggregations of vessels with enough protecting cruisers to overwhelm any raiders which the enemy might send against them. The merchantmen were not required to sail in any particular formation, nor were they required to manoeuvre against unseen mysterious foes. Neither was it absolutely essential that they should keep constantly together; and they could even spread themselves somewhat loosely over the ocean. If an enemy raider appeared on the horizon, the escorting cruiser or cruisers left the convoy and began chase; a battle ensued, the convoy meanwhile passing on its voyage unharmed. When its protecting vessels had disposed of the attackers, they rejoined the merchantmen. No unusual seamanship was demanded of the merchant captains, for the whole responsibility for their safety rested with the escorting cruisers.