pillbox, small, low fortification that houses machine guns and antitank weapons. Similar to a blockhouse, it is usually made of concrete, steel, logs, or filled sandbags. Pillboxes came into use during the early 20th cent. in the Belgian and French fortresses that were built before World War I. They were first used extensively by the Japanese in World War II. The Germans employed pillboxes in the defense of Normandy and the Siegfried Line and developed a portable steel pillbox that was used in Italy.