Sea lines of communication

China’s Critical Sea Lines of Communication. In 2004, over 80 percent of Chinese crude oil imports transited the Straits of Malacca, with less than 2 percent transiting the Straits of Lombok. Click to enlarge.

Sea lines of communication (abbreviated as SLOC) is a term describing the primary maritime routes between ports, used for trade, logistics and naval forces. It is generally used in reference to naval operations to ensure that SLOCs are open, or in times of war, to close them.

In the American Revolutionary war and the Napoleonic Wars, the SLOCs were for the most part, in the control of the British Navy—when the British lost control of them during the Revolution, the result was the loss of Yorktown and its biggest army, and ultimately the war. In the Napoleonic era, maintaining belligerence throughout, the British embargoed and blockaded any country associated with Napoleon, creating large economic hardships and dislocations that ultimately led to the people of France becoming disenchanted with their Emperor.

In World War I and World War II, the Kriegsmarine attempted to close the SLOCs from North America to the British Isles with the use of submarines. In the first, the British operated a naval blockade of Germany cutting off external trade by sea. In the second, the Allies engaged in a defensive campaign employing escort vessels and convoys to keep these SLOCs open. During World War II, the U.S. Navy successfully closed the SLOCs to Japan, strangling the resource-poor island nation.

Had the Cold War turned hot, Europe would have required resupply and reinforcement from North America. Soviet Navy strategy was to close these SLOCs in order to maximize their numerical superiority on the European continent.

See also

• Choke point
• Line of communication
• String of Pearls (China)