Short answers, pulled from the story.
The Battle of the Bulge began on the 16th of December 1944 and ended on the 25th of January 1945. This conflict lasted for over a month and became the largest and bloodiest single battle fought by the United States in World War II.
Field Marshal Gerd von Rundstedt and General Walter Model commanded the German forces during the Battle of the Bulge. The German 6th Panzer Army was led by SS Sepp Dietrich and included elite units like the 1st SS Panzer Division Leibstandarte SS Adolf Hitler.
On the 17th of December 1944, SS-Obersturmbannführer Joachim Peiper and his forces murdered at least 84 U.S. prisoners of war at the crossroads of Baugnez. The perpetrators were never punished for this crime, which became a symbol of the brutality of the war.
The 101st Airborne Division, reinforced by elements from the 9th and 10th Armored Divisions, defended Bastogne during the Battle of the Bulge. Brig. Gen. Anthony McAuliffe acted as the commander of the 101st and famously refused the German surrender request.
The Battle of the Bulge was a surprise offensive because the Allies left the Ardennes region thinly defended and believed the terrain and weather would protect them. Heavy overcast skies grounded Allied aircraft, preventing aerial reconnaissance and allowing the German army to prepare a massive attack without detection.