This is coolbert:
From the book "Roosevelts's Secret War by Joseph E. Persico:
"When U-boat torpedoes sank two average-size cargo vessels and one tanker loaded with American supplies bound for Britain, the loss amounted to approximately 42 tanks, and 428 tons of tank parts and supplies, 236 artillery pieces, 24 armored cards, 5,210 tons of ammunition, 600 rifles, 2000 tons of stores, and 1,000 tank loads of gasoline. To achieve similar destruction by bombing, it was estimated the enemy would have to conduct 3,000 sorties."
This is those days immediately following Pearl Harbor, that U-boat menace as of that exact moment a threat undiminished and also for which there was no work-able counter-measures as needed and implemented.
And we have to be crystal clear about this. ONE submarine firing probably less than a dozen torpedoes in one single action able to accomplish what entire armadas of bomber aircraft might ONLY succeed after an enormous and probably costly effort!
That ill-fated PQ-17 convoy sailing to Murmansk carrying enough war munitions and supplies to equip an army of 50,000 men, German attack by aerial bombardment, submarine and surface vessels frenzied in nature and with good reason.
Recall also that during the duration of the war there were about forty such PQ sailings, the danger from enemy attack and the weather most extreme!
Those merchant vessels laden with war munitions and associated cargoi representing a concentrated target of immense value the loss of which was not easily replaced!
It is with good reason that Churchill considered the Battle of the Atlantic as most crucial to ultimate victory and obviously so.
That American effort to supply the British and Soviet allies and OTHERS during the war a colossal endeavor for the most part overwhelming successful and should be recognized as being so!