Short answers, pulled from the story.
The ground offensive for Operation Queen began on the 16th of November 1944 after delays from earlier planned dates. Initial starting dates set for the 5th of November and later the 10th of November were delayed until the 16th of November due to bad weather.
General Omar Bradley commanded the 12th Army Group overseeing First and Ninth U.S. Armies during Operation Queen. VII Corps under J. Lawton Collins led the attack with the 1st Infantry Division and 104th Infantry Division through the Hürtgen Forest.
Total fighting cost Americans about 32,000 men since September during the operation. The 1st Division suffered about 6,000 casualties by early December before pushing out of the forest while the 4th Infantry Division lost about 6,000 men.
Germans launched their final all-out offensive Wacht am Rhein on the 16th of December 1944 on the western front. This event caused an immediate end of all Allied offensive efforts in this sector and led to the Battle of the Bulge.
Control over dams on the Roer allowed Germans to release water and flood the valley downstream as far as the Meuse. Flooding would destroy Allied bridges and isolate all troops east of the river until Allies could seize them later.