The term Guerre De Course describes a form of maritime warfare aimed at disrupting seaborne commerce. Derived from the French word for “privateer” (course), it is usually rendered as “commerce raiding” in English. Operationally, guerre de course resembles blockades in that it is primarily a form of economic warfare, in which combat with enemy warships is at best a secondary consideration. Tactically, however, its methods differ from those of a blockade. Blockades seek to apply continuous pressure, either along the entire coastline of the enemy or at key chokepoints through which ships must pass on their way to the open sea. Blockades succeed less by sinking or seizing enemy vessels than by discouraging them from embarking in the first place. If a blockade is to endure for any length of time, it always requires the deployment of forces markedly superior to those of one's adversary.

Guerre de course, in contrast, is usually adopted by countries too weak to attempt such continuous, large‐scale operations; or unwilling to risk the kind of fleet action that may be necessary to impose or break a blockade. It is conducted by individual ships (naval warships or privately owned ships armed with guns and authorized by government letters of marque to engage in legal privateering) or small squadrons. These operate in hit‐and‐run fashion along oceanic shipping lanes, or in coastal or archipelagic waters, where geography affords some means of escape should superior naval forces appear. Strategically, guerre de course represents an alternative to operations directed against the main naval forces of the enemy. Guerre de course in the form of privateering was widely employed by Americans in the Revolutionary War and the War of 1812.

Fundamentally attritional in nature, guerre de course aims to erode the enemy's warmaking capacity by depriving it of materiel, financial assistance, or military support from overseas; to undermine public morale by inflicting economic losses and depriving the population of necessary or familiar goods; and to divert a disproportionate share of the enemy's naval strength, which might otherwise be employed in more aggressive operations. It normally requires several warships, and sometimes a great many, to find and sink a single commerce raider—an imbalance that arises regardless of whether one seeks to hunt down the raiders or simply to fend them off by means of convoys. In theory, defense against a vigorously conducted guerre de course might stretch the resources of a superior navy to the point where it could not conduct offensive operations of its own. In practice, it at least affords a cost‐effective means of harassment, one whose psychological impact usually exceeds whatever material results are achieved.

Guerre de course is most frequently attempted as a counter to an enemy‐imposed blockade. During the Civil War, Confederate privateers conducted long‐range sweeps against Union shipping around the world, in order to disrupt northern trade and draw off Union warships that might otherwise have contributed to the blockade of southern ports. The exploits of the Confederate raiders became legendary. The most famous was the British‐built Alabama, an eight‐gun Barkentine‐rigged, sail and steam ship that roamed the high seas for 22 months, seizing or sinking nearly 70 Union merchantmen along the way until it was sunk by the USS Kearsarge in June 1864. By the end of the war, more than a third of all northern seaborne trade had been shifted to neutral‐flag vessels, a tribute to the predatory brilliance of men like Raphael Semmes, the Alabama's captain. (After the war, in the Alabama claims, an arbitration panel awarded the United States $15 million for merchant ships sunk by Confederate raiders built in British shipyards.)

Like Sir Francis Drake, Semmes was a private individual sailing what amounted to an armed merchantman (albeit under the Confederate flag) rather than a commissioned officer commanding a naval warship. To that extent, he was a figure of the past. The peace settlement that ended the Crimean War in 1856 included a declaration outlawing commerce raiding by irregular forces or privateers—a declaration the United States had refused to ratify because it believed efforts to codify the guerre de course favored the large professional navies of Europe over the American privateering tradition.

From the outset of the Industrial Revolution, however, it had been clear that the rising value of world maritime trade would make it an increasingly important target for regular navies; and also that such attacks would come in for an increasing share of legal scrutiny. The Declaration of 1856 was but the first in a series of attempts (including at the Hague Peace Conferences of 1899 and 1907, and the London Naval Conference in 1908) to make explicit the rights and obligations of all those caught up in a form of warfare that was, by definition, directed against unarmed ships crewed by civilians.

These matters were rendered vastly more weighty in the twentieth century by the advent of torpedo‐armed submarines, which brought to the guerre de course a ferocity and decisiveness it had not previously possessed. A surface cruiser operating under the rules of engagement accepted by nineteenth‐century navies was expected to board a prospective target, determine if its nationality and cargo made it a legal prize, and see to the safety of the crew before taking further action. However, the early months of World War I revealed that similar conduct by German submarines exposed them to enormous risks, and reduced their tactical effectiveness far below what was possible if such scruples were set aside. Guerre de course accordingly lost its traditional character as a relatively bloodless and vaguely romantic sort of peripheral operation, and became a desperate and murderous struggle capable of deciding a major war.

This trend culminated in the devastating campaign against Japanese commerce conducted by American submarines (and to a lesser extent by carrier‐based aircraft) during World War II—a rare example of guerre de course waged by the stronger side, but also suggestive of the degree to which the tactic was now losing its distinctiveness, and its historic rationale. By 1945, guerre de course had become little more than one of the modalities of total war, and scarcely the most efficient, given the capabilities of modern airpower. No first‐class navy today regards the maritime trade of its adversary as an important target, and no second‐class navy, facing a strong opponent, would consider it a feasible or fruitful one. If the spirit of Drake and Semmes survives, it does so in the small diesel submarines and fast, well‐armed patrol boats that increasingly populate the littoral regions of the world—vessels whose targets, in all probability, will be not the commerce but the capital ships of their foe.
[See also Confederate Navy; Privateering; World War II: U.S. Naval Operations in: The Pacific.]

Bibliography

Stuart L. Bernath , Squall Across the Atlantic, 1970.
Ernest Andrade, Jr. , Submarine Policy in the United States Navy, 1919–1941, Military Affairs 35/2 (April 1971).
D. P. O'Connell , The Influence of Law on Sea Power, 1975.
William M. Robinson, Jr. , The Confederate Privateers, 1990.

Daniel Moran