The Winter Line was a series of German and Italian military fortifications in Italy, constructed during World War II by Organisation Todt and commanded by Albert Kesselring. The series of three lines was designed to defend a western section of Italy, focused around the town of Monte Cassino, through which ran the important Highway 6 which led uninterrupted to Rome. The primary Gustav Line ran across Italy from just north of where the Garigliano River flows into the Tyrrhenian Sea in the west, through the Apennine Mountains to the mouth of the Sangro River on the Adriatic coast in the east. The two subsidiary lines, the Bernhardt Line and the Hitler Line, ran much shorter distances from the Tyrrehnian Sea to just northeast of Cassino where they would merge into the Gustav Line. Relative to the Gustav Line, the Hitler Line stood to the northwest and the Bernhardt Line to the southeast of the primary defenses.