Part of the Atlantic Wall defenses of Festung Europa (“Fortress Europe”) in World War II, Rommelspargel ("Rommel's Asparagus") were wooden logs driven into open fields along the French coastal plains in Normandy and Southern France. They were designed to damage gliders landing in the fields. Thousands of these poles were ordered in place by Field Marshal Erwin Rommel. In some fields, the poles were fifteen to forty feet apart and wired to mines placed on top of the poles. Hitting one pole would trigger mines all around the glider.
The logs in fact did extensive damage to the Allied gliders themselves, and also induced glider pilots to evade them and land in flooded fields, where many soldiers drowned. The Nazis' elaborately prepared defenses, however, were not nearly as effective as impromptu field fortifications based on ancient Norman hedgerows. German panzer units, with their superior mobility, firepower, training and experience, made good use of whatever defensive advantage the terrain presented. The Allies had to use air superiority and overwhelming numbers to prevail in the Normandy invasion.
Photograph: http://www.ww2gp.org/SouthernFrance.htm