Short answers, pulled from the story.
Operation Queen began on the 16th of November 1944. Its objective was to advance the U.S. First and Ninth Armies to the River Roer as a staging point for a subsequent thrust over the river to the Rhine, with the longer-term goal of establishing bridgeheads at Krefeld and Düsseldorf.
The opening air campaign employed more than 4,500 aircraft, making it one of the largest Allied tactical bombings of the war. On the 16th of November, 1,204 heavy bombers of the U.S. 8th Air Force dropped 4,120 bombs on their targets, while 467 British heavy bombers struck Düren and Jülich simultaneously.
Allied forces encountered unexpectedly heavy German resistance, particularly in the Hürtgen Forest where dense terrain rendered artillery and air support ineffective. German commanders were deliberately holding the Roer river line to protect preparations for the Ardennes Offensive, sacrificing ground only when necessary to preserve forces for that larger plan.
The Germans controlled dams on the Roer that could flood the river valley as far as the Meuse, destroying Allied bridges and trapping any forces that had crossed east of the river. Allied planners were slow to recognize this threat, making their first specific moves against the dams only in early December. The dams remained in German hands when the operation ended.
Casualties were severe across all formations. The Ninth Army suffered 1,133 killed, 6,864 wounded and 2,059 missing. VII Corps alone incurred approximately 27,000 casualties in one month of fighting, and the broader Hürtgen Forest campaign dating back to September had cost the Americans roughly 32,000 men by early December.
German commanders planned the Ardennes Offensive, codenamed Wacht am Rhein, in secret throughout the autumn of 1944, holding their best divisions back from the fighting while using depleted forces to delay the Allied advance to the Roer. On the 16th of December 1944, the same day VII Corps finally reached the Roer, the Germans launched the Ardennes Offensive, immediately stopping all Allied offensive operations in the sector until February 1945.