Shipping in and out of Danish and Norwegian ports was placed under observation and over 150,000 tons of shipping was destroyed as a result. Agents in Norway and Denmark successfully penetrated their military thoroughly enough to determine the disposition and strength of land forces in both countries and deep-cover Abwehr operatives kept the German forces, particularly the Luftwaffe, intimately informed during the invasion of Norway. Against both of these nations, the Abwehr mounted what one would call a successful intelligence operation of some scale and proved itself critical to the success of German military endeavors there.[42]