1st Phase - September 1939 to Fall of France
Donitz had 57 subs; British had radar, asdic (location fixed by time of return "ping")
Sept. 3 - U30 sank British liner Athenia - 1st sinking of the war by a German Unterseeboot ("U-boat")
Sept. 5 - Gunther Prien, "Bull of Scapa Flow", sank the Bosnia, 1st cargo ship sunk in war
Sept. 6 - 1st convoy - 36 ships in 9 parallel rows of 4 each, 1 escort in front, left, right
Oct. 11 - SS Iroquois arrived safely in New York.
May 5, 1940 - Germany captured HMS Seal, codes for B-dienst; copied its torpedo design
2nd Phase - June 1940 to Lend-Lease
Donitz had 21 operational subs and began wolf-packs; British increased escort ships to 375
sub pens in France, from Time 1942
June 22 - fall of France; 1st sub base at Lorient operated July 6, construction began of thick concrete pens to protect subs from air attack
Aug. 17 - Hitler proclaimed total blockade of England to all shipping
Oct 18-19 - wolf-pack of 6 subs sank 36 of 79 in 2 convoys - 2 worst days of war
Oct. - "The Happy Time" for subs - record average sinking of 60,000 tons per month per sub
March 11, 1941 - Lend-lease approved; North Atlantic route became most important
3rd Phase - April 1941 to Pearl Harbor
Donitz fleet grew to 249 subs with 35 operational; British Ultra cracked sub codes, a triumph of WWII code breaking; see NSA 1980 study "Ultra and the Campaign against the German U-boat"
Apr. 11 - U.S. destroyer Niblack fired 1st U.S. shot in the war, in widened Security Zone
Apr. 17 - Neutral Egyptian freighter ZamZam sunk by German cruiser Atlantic, 138 Americans rescued.
May 9 - British destroyer Bulldog south of Iceland captured U-110 sub and its Enigma machine
June 20 - FDR speech on the SS Robin Moor sunk by U-69 May 21; sub 0-9 lost in accident
May 27 - HX129 convoy first to be escorted "end-to-end" across Atlantic; Canadian Navy joins
July 1 - FDR includes Iceland in the security zone, sends marines, crosses the threshold to undeclared naval war in the Atlantic
Aug. 1 - first convoy to Murmansk - Atlantic route doubly important, helped Russians and British
Sept. 16 - HX150 from Halifax was the first convoy with American escorts to Iceland
Oct. 19 - SS Lehigh sunk off African coast by U-126
Oct. 27 - U-96 departed St. Nazaire on its 7th patrol, source of film Das Boot
Oct. 31 - U.S. destroyer Reuben James sunk
Dec. 7 - U.S. built Audacity-class escort carriers, Liberty ships, B-24 with 24 depth charges
4th Phase - January 1942 to destruction of PQ17
Donitz fleet grew to 331 subs with 140 operational; Brit. & Canada providing 98% of all escorts
Jan-Mar. - 2nd "Happy Time" for German subs that sank 216 ships off U.S. East coast, mostly oil tankers.
Jan. 13 - Operation Drumbeat was the first of several waves of German sub attacks on the U.S. eastern seaboard; in this first wave, 5 German type IXB long-range U-boats sank 25 ships by Feb. 6.
Feb. 1 - Germans changed to Triton cipher; no Ultras until after the British captured codebooks on the U-559 Oct. 30, 1942, one of the events that inspired the film U-571.
Feb. 9 - The luxury liner Normandie mysteriously burned in New York harbor; ONI feared German subs were landing saboteurs and recruited Luciano to use the longshoremen to stop sabotage, and to get Joe Lanza's fishermen to report U-boat locations.
March 28 - 1st "milch-cows" supply German subs at sea; by May, supply ships off Bermuda extended the patrols of type IXB boats to 8 weeks and smaller type VII boats to 4 weeks.
May 14 - U.S. finally started convoys and blackouts along East coast.
June - worst month of war for shipping losses = 834,196 tons
July - first month that replacement shipping started to exceed losses
July 5 - PQ17 to Murmansk lost 23 of 36 ships to subs and Kondors, the worst single convoy loss of war.
5th Phase - July 1942 to Donitz Withdrawal
Donitz had 393 subs, 212 operational (peak of 240 Apr. 1); Allies equipped planes with 10 cm. radar
July 19 - Donitz recalled the last 2 subs from the U.S. eastern coast in order to concentrate on the North Atlantic.
Aug. 22 - Brazil declared war on Germany after sub attacks; Allies controlled "waist" of Atlantic.
Sept.-Dec. - "deliberate weakening" of Atlantic defenses to supply TORCH.
Jan. 8, 1943 - TM1 lost 7 of 9 oil tankers and 100,000 tons oil for TORCH.
Jan. 24 - Casablanca decision to give Atlantic war highest priority to defeat "U-boats"
Feb. - FDR overruled King and allocated 250 aircraft for Atlantic, created 10th Fleet in May 1.
May - Donitz lost 43 subs, twice the replacement rate; only sank 34 Allied ships in the Atlantic.
May 24 - Donitz ordered all subs out of North Atlantic; 45-month campaign came to an end.
6th Phase - June 1943 to May 1945
Donitz tried new technologies but failed; Allies developed magnetic detector, began to bomb sub factories
Sept., 1943 - Lether group entered North Atlantic with new anti-radar devices but failed.
Jan. 1944 - Donitz sent out 2 groups with new schnorkel breathing device but both were attacked.
May 1944 - Donitz restricted schnorkel subs to immediate waters around England to avoid radar.
Feb. 11, 1945 - Coast Guard escort Howard D. Crow sank the U-869 off New Jersey, a "lost" sub described in the book Shadow Divers Feb. 25, 1945 - new electric-powered sub sank 1st ship and easily escaped underwater at 20 knots.
April 1945 - Seewolf group of 6 type IXC boats with schnokels was sent to U.S. east coast in the last German attempt to attack convoys; U.S. responded with 4 escort carrier groups in Operation Teardrop that destroyed 5 of 6 subs.
May 23, 1945 - Donitz arrested; during the war he built 1162 subs, 830 in operation, that sank 5150 ships and 21m tons.
This timeline was posted to the University of San Diego website in January 2002 and appears to be copyright Steve Schoenherr. It was taken down in 2010, whereupon I copied it to this website.