Field telephones operate over wire lines, sometimes commandeering civilian circuits when available, but often using wires strung in combat conditions. At least as of World War II, wire communications were the preferred method for the U.S. Army, with radio use only when needed, e.g. to communicate with mobile units, or until wires could be set up. Field phones could operate point to point or via a switchboard at a command post. A variety of wire types are used, ranging from light weight "assault wire," e.g. W-130 —— with a talking range about , to heavier cable with multiple pairs. Equipment for laying the wire ranges from reels on backpacks to trucks equipped with plows to bury lines.