Since I'm writing, (or trying to write,) an AH novel about this, I'll take a crack
at it. The Abwehr, German Military Intelligence, under the leadership of Admiral Wilhelm Canaris, through agents in Spain and Portugal, obtains the
plans for Operation Torch. These agents send them to the German Embassy
in Madrid, which forwards them to Berlin, and they end up in Canaris' hands.
Canaris then sends them to Hitler. Hitler decides that the American contingent,
half of which is leaving from the East Coast of the United States, and half of
which is leaving from Britain, has to be destroyed. He orders his U-boats,
E-boats, and Germany's aircraft carrier, Deutschland, to intercept the
American invasion force in the Mid-Atlantic, and the commander of the German task force, Admiral Gunther Lutjens, orders his navalized Me. 109s and Stukas, into the air to sink the American ships. The German battleship
Bismarck, and cruiser Prinz Eugen, which are part of the German
Mediterranean Fleet, based at Malta, harass the Allies. They sink Allied ships
trying to resupply the Allies in North Africa. Rommel had defeated Montgomery at El Alamein and captured the entire British Eighth Army.