The first British response to the submarine, dating from the start of the war and intensified in 1916, included a number of measures. The British navy set down extensive minefields to block German submarines from leaving their harbors. A barrier based on nets as well as mines was set up in the English Channel. Merchant ships received naval guns to defend themselves, and the navy employed decoy vessels known as Q ships. These appeared to be merchant ships, but they were actually vessels designed to attack U-boats; manned by naval crews with hidden armaments, they tried to make the submarines surface and approach so that the hunter could be transformed into the hunted. Nonetheless, the lords of the Admiralty and most combat commanders favored a different countermeasure: patrolling key sea lanes with warships. This requires some explanation. For centuries, the island nation's navy had protected wartime commerce by a different method: escorting convoys of merchant vessels. But this practice had fallen into disfavor during a century without naval warfare after Britain's 1805 victory over France at Trafalgar. Doctrines of free trade made ship owners reluctant to put their vessels under government control, even in moments of peril. The speed of merchant vessels in the new era of steam power seemed to offer adequate protection against attack. Most important of all, the offensive naval doctrines of theorists like American admiral Alfred Thayer Mahan proclaimed that the duty of a fighting navy was to seek out and destroy the enemy's main fleet. Patrolling the sea lanes to seek out the submarines appeared consistent with this offensive mind-set. Thus, the navy discarded the protecfion of commerce, and it did so for reasons of doctrine, even for reasons of psychology. To hunt the enemy down was proper; to shield merchant convoys was almost cowardly. As Trevor Wilson has remarked, British leaders failed to see that "the way to counter submarines was not by going in search of them but by standing between them and their quaiTy." Unfortunately, the patrols encountered few submarines, and sank even fewer, as losses of merchant ships continued to mount. Even the most aggressive patrolling amounted to nothing more than watching the ocean. As the war went on, the navy accepted a limited use of convoys, especially for transporting troops and particularly valuable individual ships. But most naval authorities rejected their wider use.