Germany’s U-boat campaign was meant to force Britain out of the war. It has failed. The Germans underestimated the resilience of the British to shipping losses but they also failed to anticipate Allied countermeasures against the U-boats. Allied ships are now increasingly sailing in convoys, guarded from the U-boats by warships. The U-boats have great difficulties pressing attacks against ships in convoys, with the result that Allied shipping losses have declined. In October the U-boats managed to sink around 460,000 tonnes of Allied shipping, still an impressive figure but well below the over-optimistic target of 600,000 tonnes projected as being needed each month to force Britain to make peace.
The escalated U-boat campaign, and Allied countermeasures against it, is also taking its toll on the U-boat crews. Not merely are they being worked to exhaustion, they have also seen their own losses spiral upwards from those of the previous year. The submariners are giving their all, but for naught.
U-boat and crew (Eurasia Times: WWI U-boat found off Belgium)