blockade, use of naval forces to cut off maritime communication and supply. Blockades may be used to prevent shipping from reaching enemy ports, or they may serve purposes of coercion. The term is rarely applied to land sieges. During the Napoleonic wars, both France and Great Britain attempted to control neutral commerce through blockades and embargoes which neither could enforce with sufficient rigor. The Declaration of Paris (see Paris, Declaration of) proclaimed (1856) that blockades were henceforth to be announced to all affected parties and would be legal only if effectively enforced against all neutrals. In both World Wars blockades were made more effective by the employment, in addition to naval vessels, of mines and aircraft. North Vietnamese ports were mined and blockaded by the United States during later stages of the Vietnam War. Blockades have also occasionally been employed in times of peace as threats to implement diplomacy, as in the blockade of Cuba by the United States in 1962.