The Battle Of The Atlantic

[Sailor Steve]

The Asdic Myth

The faithful effort has relieved us of our great danger...that our methods are now so efficient that we will need fewer destroyers in the North Sea and the Mediterranean.
-Winston Churchill, 1936

So important is the development of Asdic that the submarine should never again be able to present us with the problem we were faced with in 1917...one destroyer could do the work of a whole flotilla.
-Admiralty Report

What I didn't know before was that early Asdic sets didn't even have screens. It was up to the skill of the operator to interpret the time between signal and return, and estimate the range to the target. Also, echoes were obtained from schools of fish, whales, wrecks, the sea bed or even different layers of water. We know that thermal layers could be useful, but the fact appears to be that Asdic was not nearly as reliable as the escorts would have liked. Also, in September 1939 only about 1 in 10 destroyers had it at all.