Installations, works and demolitions designed to prevent or hinder the movement of forces. They are put in place in order to inflict losses on the enemy, to delay or hamper his movements and actions, to restrict his manoeuvres or to force him to advance in a direction favourable to friendly forces. They may be subdivided by type into explosive, non-explosive, electrified and combined obstacles, by location and purpose into land, air or sea obstacles and by scale into operational or tactical obstacles

: 27 phrases in 13 subjects