Convoys and Escort Ships for Defense

Travel across the Atlantic to England

An Atlantic convoy. U.S. Navy photo.

LSTs and other supply ships traveled across the Atlantic to England, in preparation for various assaults upon the Axis. These ships were scheduled to sail in convoys and the Navy made efforts to assign escorts so there would be some defense. But because of the shortage of escort ships in the first half of the war, convoys that were scheduled to have three or four escorts, often received only one or two when there were simply not enough to go around. And of course, when the number of escorts drops below about 4 or 5, it becomes much more difficult to protect the entire convoy from all four corners. If there is not an escort vessel on each corner using its sonar, prepared to move quickly to drop depth charges, then it becomes that much easier for a U-boat to slip in at night and attack the convoys.

Speed Comparison - Convoy Ships, U-boats, & Escorts Ships

A comparison of speeds of the various ships will help put this into perspective. Convoys were typically traveling at a speed between 8-10 mph. A surfaced U-boat could travel approximately 17-19 mph. So even though the submarines were only going 8-9 mph when submerged, once they got up on the surface, they became significantly faster. This fact gave them a way of overtaking convoys which had been located.

In contrast, the escort ships normally protecting the convoy (escort carriers, corvettes frigates, and sloops), had a range of speeds approximately 16-25 mph. Some destroyers could actually reach 38 mph, but these were in short supply. A convoy ranged between 20 to 60 cargo ships, and would ideally have five or six escort vessels. However, often only two warships were available early in the war, which proved to be inadequate protection.