Short answers, pulled from the story.
The German army launched the offensive on the 16th of December 1944 under the code name Operation Watch on the Rhine. This massive attack targeted the Ardennes forest to split Allied forces and capture the port of Antwerp.
Field Marshal Gerd von Rundstedt and Walter Model led the operation despite doubting its chances of success from the start. Hitler ignored their warnings and insisted on the original plan which relied on surprise and bad weather to ground American aircraft.
SS troopers opened fire on American prisoners near Baugnez crossroads at 12:30 PM on the 17th of December 1944 and murdered about 84 men after they surrendered. Another smaller massacre occurred in Wereth Belgium on the same day where eleven black American soldiers were tortured before being executed by men of the 1st SS Panzer Division.
General Anthony McAuliffe received a demand for surrender from German commander Lüttwitz and responded with frustration using the word Nuts. His staff typed up the reply which became famous among troops and served as a morale booster during the siege.
The lead element of Patton's Third Army reached Bastogne ending the siege on the 26th of December 1945. Company D of the 37th Tank Battalion broke through at 16:50 that evening to relieve the trapped units.