Raiders ~ Auxiliary / Merchantmen / Commerce

Auxiliary cruisers, aka armed merchantmen, were merchant ships converted into armed vessels and employed either for convoy protection or commerce raiding. In the latter role, they were disguised as merchant ships, but equipped with hidden cruiser-size guns, false funnels, torpedo tubes, mines, float planes for scouting and wore false colors, markings and flags. Their appearance was used to trick enemy merchant ships into approaching thinking they were but harmless steamers. Their speed, combined with their float planes, enabled them to search large areas of ocean for prey. Once located, the auxiliary cruiser's big guns could defeat any merchant or smaller combatant.

In the days of sail, piracy and privateers, many merchantmen would be routinely armed, especially those engaging in long distance and high value trade. The most famous of this type were the East Indiamen able to defeat regular warships in battle (see Battle of Pulo Aura).

In more modern times, auxiliary cruisers were used offensively to disrupt trade chiefly during both WWI and WWII, particularly by Germany.

Commerce raiding is a form of naval warfare used to destroy or disrupt logistics of the enemy on the open sea by attacking its merchant shipping, rather than engaging its combatants or enforcing a blockade against them. It is also known, in French, as guerre de course (literally, "war of the chase") and, in German, Handelskrieg ("trade war"), from the nations most heavily committed to it historically as a strategy.

Commerce raiding was heavily criticized by the naval theorist A.T. Mahan, who regarded it as a distraction from the destruction of the enemy's fighting power. Nevertheless, commerce raiding was an important part of naval strategy from the Early Modern period through WWII.

Usually, commerce raiding is chosen by a weaker naval power against a stronger, or by a nation with little ocean-going trade against one with a great deal. The best protection against a commerce raiding strategy is for merchant vessels to sail in convoy, protected by naval escorts.