 It was composed of an intricate system of strong points, fortifications and military facilities such as border guard posts, communications centres, infantry shelters, barricades, artillery, machine gun and anti-tank gun emplacements, supply depots, infrastructure facilities and observation posts.These various structures reinforced a "principal line of resistance" made up of the most heavily armed "ouvrages", which can be roughly translated as fortresses or big defensive works.From front to rear, (east to west) the line was composed of