The direct attack on the German positions in and around San Pietro began on December 8 by II Corps of the Fifth Army. The positions were defended by the second and third battalions of the 15th Panzer Grenadier Regiment and the second battalion of the 71st Panzer Grenadier Regiment, all part of German Tenth Army's XIV Panzer Corps.
After a week of intense attacks and counter-attacks the US 36th Division's 143rd Infantry Regiment and the 504th Parachute Infantry Regiment commanded the heights of the Sambùcaro mass. The US 36th
Division, then planned a further effort for 15 December. 143rd Infantry assisted by 504th PIB would continue to push west along the shoulders of Sambùcaro and take San Vittore del Lazio while to the south of Route 6 142nd Infantry Regiment supported by the Italian 1st Mororized Group were to capture Mount Lungo. In the center 141st Infantry would attack San Pietro itself. The main attack of the 36th Division started at 1200 on 15 December. After four successive Allied attacks and German counter-attacks, the Germans pulled back from San Pietro since the dominating ground on both flanks, Mount Lungo and the Sambùcaro peaks, was now in II Corps' possession. The Germans launched a counter-attack on December 16 to cover their withdrawal as they retreated to positions farther north at Cedro Hill, Mount Porchia, San Vittore, and the western spurs of Sambúcaro