Why the anti-submarine balance shifted in 1943

The tonnage charts compare U-boat sinkings with the much higher German targets needed to break Allied shipping. Results rose above the post-American-entry target only twice, helped by the opportunity along the American seaboard, before dropping sharply in 1943. Centimetric radar and other improvements increased Allied anti-submarine capability. Rising U-boat losses mattered alongside falling merchant losses because increasingly effective detection and attack forced German tactics to change.