The campaign in Northwest Europe has been the subject of thousands of books and articles, including a number based on careful documentary research. But even the best accounts pay insufficient attention to the German weapons systems that inflicted the majority of Allied casualties. The mortar and the Nebelwerfer were chiefly responsible for the Wehrmacht’s temporary success in stablizing the front in Normandy, and for the balance of the war they played a major role in demoralizing and reducing the strength of Allied infantry units. The Allies did not foresee the central role these weapons would play in Northwest Europe and all three armies left counter-mortar operations to the initiative of individual divisional commanders.
This paper focuses on the work of 21 Army Group’s No. 2 Operational Research Section (ORS) in developing a systematic and ultimately successful system of neutralizing enemy mortar and Nebelwerfer fire. Other attempts to deal with the problem were undertaken concurrently in the Mediterranean theatre and in First American Army but they are not examined here.
Copp, Terry "Counter-Mortar Operational Research in the 21 Army Group." Canadian Military History 3, 2 (1994)