99th Infantry Division used the relatively quiet period to prepare an extensive defensive system, including redundant lines of communication, precise positioning of weapons to provide interlocking grazing fire, and aggressive patrols that kept the Germans off guard. They also carefully integrated artillery support; registered on likely targets based on probable enemy approaches. 393rd Regiment held the center and 394th watched over the south. By mid-December, the troops were well dug in and had wired their positions with barbed wire and trip flares. They covered their fox holes with felled timber. The weather was unusually calm and cold. Between 19 December 1944 and 31 January 1945, the average maximum temperature at the front lines in Europe was 33.5 °F. (0.83 °C.), and the average minimum temperature 22.6 °F. (−5.2 °C.).