Within the Avocourt-Malancourt sector, the Germans held one of their most formidable positions on the entire Western Front...On the horizon, the dominating heights of Montfaucon rose threateningly. It was from these heights that the German Crown Prince had observed the futile assaults upon Verdun two years before. So strong was this position (enhanced by superb fortifications, a commanding view, and covered by excellent fields of fire) that the Germans called Montfaucon the "Little Gibraltar" and boasted that it could never be taken. Strong as the enemy positions were by nature, the Boche had rendered them still more formidable by four years of ceaseless labor, constructing trenches, gun positions, entanglements, and pill boxes to cover every conceivable approach the Allied forces might use in an attack.
From: U.S. Army Battle Analysis, "The Battle of Montfaucon," Command and General Staff College