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"Convoy" (Middleton?) is a very good book about March 43. There were actually 3 eastbound convoys at sea covered by the book: HX229, HX229A,and SC107. March 43 was the time when convoys began to get very long range aircraft coverage of the Greenland Air Gap. The results were immediate.


In addition both the USN and the USAAF changed their tactics: rather than hunting submarines just any old place they started to commit modern DDs/DEs to hunting submarines near the convoys and forming more (convoy) Support Groups and CVE Hunter-Killer Groups. The USAAF spent 1942 bouncing their bombs off of the sub pens in France. Committing the initially limited number of long range bombers to support of the convoys worked much better.

Also previously the USN tended to view ASW as defensive (similar to the IJN) and committed only the oldest DDs and a few USCG cutters to convoy escort duties (where by 1943 they were getting overwhelmed by the relative hordes of Uboats).

ORIGINAL: spence

"Convoy" (Middleton?) is a very good book about March 43. There were actually 3 eastbound convoys at sea covered by the book: HX229, HX229A,and SC107. March 43 was the time when convoys began to get very long range aircraft coverage of the Greenland Air Gap. The results were immediate.


In addition both the USN and the USAAF changed their tactics: rather than hunting submarines just any old place they started to commit modern DDs/DEs to hunting submarines near the convoys and forming more (convoy) Support Groups and CVE Hunter-Killer Groups. The USAAF spent 1942 bouncing their bombs off of the sub pens in France. Committing the initially limited number of long range bombers to support of the convoys worked much better.

Also previously the USN tended to view ASW as defensive (similar to the IJN) and committed only the oldest DDs and a few USCG cutters to convoy escort duties (where by 1943 they were getting overwhelmed by the relative hordes of Uboats).

Yes, a number of things came together at that point in the war to finally defeat the U-boats. VLR Liberators, CVEs, DEs, Black Swan type Sloops and Frigates, HF/DF, radar on smaller escort vessels, DCs capable of 600 foot depth, better intel, better tactics, better training, etc. Did you know that scientists were hired to figure out the best D/C pattern for an attack. The optimum trade-off between effectiveness and D/C expenditure turned out to be 10: two off the racks, two from the throwers, two more off the rack, two from the throwers and a final two more from the rack.

As for the use of old vessels, the British and Commonwealth countries were in the same fix when their war started. At least the US had some time to observe what was happening and start the planning for all the ships it needed to build when the time came. The result was a flood of escorts (and merchantmen) that the Germans never imagined could happen.

The hunter-killer ASW ships also had a new electronic listening device, that could fairly accurately pinpoint exactly where the U-Boats were during their transmitting (which usually occurred around the same time of day each morning). One of the earliest and most successful ECM measures!
The U-Boats had to transmit and receive from fairl near to the surface (or on it) and were thus fairly easy to pick off.

ORIGINAL: xj900uk

The hunter-killer ASW ships also had a new electronic listening device, that could fairly accurately pinpoint exactly where the U-Boats were during their transmitting (which usually occurred around the same time of day each morning). One of the earliest and most successful ECM measures!
The U-Boats had to transmit and receive from fairl near to the surface (or on it) and were thus fairly easy to pick off.

HF/DF or "Huff Duff" - High Frequency Detection Finder Since quite early in the war these were deployed to some vessels but the number was low. Not more than one per convoy - resulting in approximately direction of the transmission available immediately for the Escort commander. Could be supplemented by land-based HF/DF detections forwarded to convoys (took time obviously).
Later two were assigned to a convoy - one for Escort commanders ship, the other for the rescue ship or some other - ships were positioned to the front and rear of the convoy so intersection of their signals could give away the position of the transmitting sub. The more carried and available to commander the better.

Support groups carried usually their own and as they were not bound to the specific convoy, their primary mission was not only to keep sub away, but to hunt it till exhaustion. Each corvette from the direct convoy escort keeping the sub under till the convoy pass along means much less protection for the ships (and the speed difference of convoy and corvette is really small when in stern-chase). On the other hand the support groups could hunt subs till they got it.

HF/DF or "Huff Duff" - High Frequency Detection Finder Since quite early in the war these were deployed to some vessels but the number was low. Not more than one per convoy - resulting in approximately direction of the transmission available immediately for the Escort commander.

HFDF existed during the First World War but the equipment was bulky and not amenable to shipboard use. Shore based HFDF stations were able to locate concentrations of Uboats by their transmissions right from the start in WW2. The importance of HFDF became much more decisive when the sets were put on ships within the convoy because the accuracy of the bearings on a signal increased substantially with the reduction in range between the transmitter and the convoy. Multiple bearings could give "a fix" on the transmitter whereas shore stations could only manage "within 25 miles of _____N, ______W (at best). Even if there was only one HFDF set in a convoy the escort could "run down the bearing" of the transmitter (since the transmitter was usually within visual sighting distance or only slightly more than what one can see from a spot a dozen ft above the sea surface - contrasted with 25-35 ft above the sea on the escort).

BTW the set pictured on the load screen in WitP:AE has a serial number approximately 211,000+ larger than the serial number on the set on my first ship: USCGC Duane, one of the ships committed to convoy escort in 1942-early 43.