What forced German submarines to retreat during World War II?

The correct answer relates to the strategic military developments that occurred during World War II, particularly in the Atlantic Ocean. The increased number of surface escorts played a significant role in combating the German U-boat threat. As the war progressed, the Allies improved their tactics and convoy systems, ensuring that merchant ships were protected by destroyers and other naval vessels, which patrolled the waters and provided a deterrent against submarine attacks.

These surface escorts were equipped with depth charges and improved weaponry, allowing them to effectively counter submarine threats. The presence of these escorts significantly decreased the U-boats' operational effectiveness, compelling German submarines to retreat or modify their tactics to minimize losses. This adaptation was crucial, as the success of Allied supply convoys directly impacted the war effort, making the presence of escorts a decisive factor in reducing the threat posed by German submarines.