The cheval de frise (plural: chevaux de frise , "Frisian horses") is a defensive obstacle, which existed in a number of forms and were employed in various applications. These included underwater constructions used to prevent the passage of ships or other vessels on rivers, or as anti-cavalry measure consisting of a portable frame (sometimes just a simple log) covered with many projecting long iron or wooden spikes or spears. They were principally intended as an anti-cavalry obstacle but could also be moved quickly to help block a breach in another barrier. They remained in occasional use until they were replaced by wire obstacles just after the American Civil War. During the Civil War, the Confederates used this type of barrier more often than the Union forces. During World War I, armies used "chevaux de frise" to temporarily plug gaps in barbed wire. Barbed wire "chevaux de frise" were used in jungle fighting on the South Pacific islands during World War II.