69 years ago today, the first of five German U-Boats sailed to begin commerce-raiding operations off the east coast of the United States.
The U-boats were able to sink so many ships with so few German losses that the period from the arrival of the U-boats to about August of 1942 became known as the "Second Happy Time".
The reaction of the US Navy to the U-boat campaign, as well as the local governments in coastal cities, bordered on criminal neglect and dereliction of duty.
The Navy fought the institution of a coastal convoy system, despite the lessons learned during both the First World War and the high losses the British suffered at the onset of the Second World War. The Navy was extremely slow to react and resisted the formation of civilian aerial antisubmarine patrols (a measure that proved to be an extremely effective countermeasure). Until the Navy pulled its collective thumb out of its ass, many merchant vessels were sunk, most with the loss of their crews.
Merchant ships sailing independently tried hopping from anchorage to anchorage, sailing only in darkness. The U-boats were able to see ships operating inshore silhouetted by the lights of towns and cities. Civilian governments resisted the institution of a coastal blackout, because the local governments feared the impact of a blackout on their merchants, preferring to see ships on the horizon burning from U-boat attacks.
Keep in mind that although the film stock from the war shows the U-boats executing torpedo attacks, U-boats sank a lot of ships by surfacing and firing on those ships with their deck guns, because submarines of the day carried maybe 12-20 torpedoes. Surfaced U-boats were vulnerable to air attack; the later formation of the Civil Air Patrol, light aircraft armed with small bombs, forced the U-boats to discontinue surface attacks.
Between the CAP flights, convoying and Navy blimp patrols, merchant sinkings went down and U-boat losses climbed, making operations off the U.S. coast a lot more hazardous for the U-boat crews.