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The US Coast Guard and Battle of the Atlantic Briefing
by Michael G Walling   
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Last edited: Monday, November 02, 2009
Posted: Monday, November 02, 2009

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Background details of the longest battle in WWII.

World War II

Atlantic Convoy Briefing


“The only thing that ever really frightened me during the war was the U-boat peril.”

                                                                                            Sir Winston Churchill

                                                                                     British Prime Minister, 1940 - 1945


            Had the Allies lost the Battle of the Atlantic it is possible that they would have lost the war in Europe.  Without supplies from the U.S. and Canada, England would have been starved into submission, the Soviet Union could not have sustained her fight, Allied troops in Africa would have been isolated, and the invasion of Normandy on June 6, 1944 would not have taken place.  In March 1943, the German Navy came within a hair’s breath of winning this battle and the consequences had this occurred staggers the imagination.

I will take a few moments to provide a brief history of the U.S. Coast Guard, the reason for convoys and their organization, tactics used by warships guarding the convoys, the U-boats and their tactics, how Military Intelligence was gathered, and descriptions of the four primary overseas naval bases the cutters operated from.


The U. S. Coast Guard

            The United States Coast Guard is the oldest continuous sea-going service of this nation.  Founded in 1790 by Alexander Hamilton, the first Secretary of the Treasury, as the Revenue Marine Cutter Service, it was originally composed of ten schooners used for the collection of custom duties and the enforcement of the revenue laws.  According to Howard I. Chapelll, the English term “cutter” was used to describe these vessels because of its association in the mind of the public with the collection of revenue.

            Following the War of Independence (1776-83), the Continental Navy was disbanded and, from 1790 until 1794 when the U.S. Navy was created, the Revenue Cutters were the only national maritime force.  The Federal Acts establishing the Navy also empowered the President to use the Revenue Cutters to supplement the Navy’s fleet when needed.  Laws later further clarified the relationship between the two services.

            The Coast Guard came into being on January 20, 1915 when Congress passed and President Wilson signed “An Act to create the Coast Guard ... which shall constitute part of the military forces of the United States.” It was formed by combining the Revenue Marine Service and the Life Saving Service.  Between 1919 and 1942, the Federal Lighthouse Service, Steamboat Inspection Service and the Bureau of Navigation were amalgamated into the Coast Guard, thus creating its present form. Although they were part of the same organization, members of both the Life Saving Service and the Light House Service were allowed to retain their own distinctive cap devices and for many years formed proud cadres of individuals within the larger service.

            The Coast Guard derives its authority for marine law enforcement and safety at sea from Articles of the United States Code.  In the 1930s the duties of the Coast Guard included the enforcement of maritime law; assistance to life and property on the sea; national defense, destruction of derelict ships and other hazards to navigation, maintenance of aids to navigation such as buoys, lightships, and shore-mounted day markers; law enforcement in Alaska, International Ice Patrol in the North Atlantic; and other operations of its cutters, aircraft and life-saving stations ashore. 

Although structured as a military service, the Coast Guard is not part of the Department of Defense.  Rather, it remained part of the Treasury Department from its inception in 1790 until 1967 then was moved to the new Department of Transportation.  Currently it is part of the Department of Homeland Security.

            The Coast Guard has traditionally performed two roles in wartime. The first has been to augment the Navy with men and cutters. The second has been to undertake special missions for which peacetime experiences had given the Service unique skills.  Among these special skills called upon in World War II was the Coast Guard’s experience working in Arctic and near Arctic conditions. 

Another skill was its expertise in maneuvering small boats safely on and off beaches through heavy surf, not something the Navy practiced.  Amphibious warfare, with the need to transport men and equipment from ships off shore to enemy-held beaches on a massive scale, was a new concept.  The Coast Guard was a major part of the newly constituted U.S. Amphibious Force which came into being in the summer of 1941.  It was Coast Guardsmen who formed the core of the crews running landing craft in over 150 invasions. 

            Starting with the quasi war with France in 1791, the Coast Guard and its forerunner the Revenue Marine Service, has provided ships and men to support the U.S. Navy in every conflict.  During World War I they were called upon to escort trans-Atlantic convoys, but even in the heat of battle, remained true to their traditional role as guardians.   

            Perhaps the finest tribute ever paid to the Coast Guard was written by Captain Joseph

Gainard in his book Yankee Skipper:


No country in the world has a Coast Guard service like that of the United States. No other nation can send ships of that kind out for an emergency, though even if they could, probably they would not.  There is no charge for the work, food and medical attention rendered by the Coast Guard, to say nothing of the comfort they give just by being around.  It is an efficient service, well manned and officered.  To be an officer in the Coast Guard and to stay there, you have to be 100 percent on the ball.  They are absolutely sailors, that is why they are all right.  A United States Coast Guard cutter, I claim, will outride anything they can ever be called to face - storm, disaster or hurricane.[1]


            The Coast Guard’s motto and tradition is “Semper Paratus” (Always Ready).  In an unbroken chain stretching backing more than two centuries, thousands of Coast Guard women and men have lived by this motto and upheld this tradition.



            Ships are the only way to move large amounts of men and material across an ocean.  In peacetime they follow well-known routes (sea-lanes) that are equivalent to interstate highways on land.  The routes vary from summer to winter dictated by the weather and ice conditions.  Over hundreds of years these sea-lanes have proven to be the best and most efficient options of sailing from one port to another.  War changed this, as both sides knew the routes and could lay ambushes along them. 

            The best way to protect merchant ships during war is to convoy them with a screen of warships for protection.  An analogy is a herd of sheep protected by sheep dogs.  Trouble comes for the sheep when there are too many predators and not enough sheep dogs.  

            Convoys varied size from as few as three ships to over a 100.  The ships were arranged in columns 1,000 yards apart (one-half a nautical mile) and each ship in that column 500 yards astern of the one in front of it.  A forty-eight ship convoy arranged in eight columns with six ships per column covered an area almost four miles wide and three and a half miles deep.  With the escort screen, the convoy would encompass about thirty-six square miles of ocean (see diagram 1).

Organizationally, a convoy was divided into two groups; the merchant ships under the direction of a civilian Convoy Commodore who had the responsibility its organization when at sea and the military Escort Commander in charge of the accompanying warships. 

The Commodore was usually a retired Navy Admiral recalled to fill the role.  He and a small staff of assistants rode on one of the merchant ships.  A major part of the Commodore’s responsibility was to retransmit any messages from the Escort Commander to the convoy regarding evasive maneuvers.   The Escort Commander did not have authority over the Commodore and could only ask for, but not order, changes in the convoy operations or arrangement.

Before leaving port, a briefing was conducted for all of the merchant ship captains. Each was given copies of the convoy organization, emergency communication instructions, copies of the zigzag patterns to be used, and a myriad of other details needed to successfully operate in company with other ships. 

There were two departure points for eastbound convoys: Halifax, Nova Scotia for the fast ones (“HX”) and Sidney, Nova Scotia for the slow ones (“SC”).  Westbound, both fast (“ON”) and slow (“ONS”) gathered close to one of the western English ports before heading out. 

            The distance from Halifax, Nova Scotia, Canada to Londonderry, Northern Island is approximately 2,500 nautical miles.  It took a slow convoy roughly seventeen days and a fast one about eight days to make the voyage.  This was in good weather.  Fog caused delays.  U-boat and aircraft attacks forced radical alterations in courses adding miles to the voyage.  Westbound convoys faced headwinds which slowed them even more.  Storms forced ships to heave-to for days at a time, damaging or disabling them and scattering a convoy over hundreds of square miles of ocean.   Each delay increased the risk of attack.

Often there were at least two convoys headed east and two or more westbound any given time.  Although it looks large, the North Atlantic is really a small place when there are hundreds of ships to get across safely and tens of U-boats trying to stop them.

When the war started in September 1939, the British Navy began to convoy merchant ships.  At the time U-boats were operating from bases in northern Germany and had to sail through the North Sea before getting to the target-rich areas off Britain’s west coast.  This long voyage used up much of a U-boat’s fuel, limiting the distance and duration of its hunting.  Because of this, it wasn’t necessary for escorts to stay with the merchant ships for more than few hundred miles west of the Irish coast.  When they were safely beyond the range of U-boats, the convoy was dispersed and each ship proceeded independently to its destination. 

            After France was signed an armistice with Germany on June 22, 1940, this situation changed dramatically.  The German Navy acquired three bases along France’s west coast at Brest, Lorient, and St. Nazaire, that offered unhindered access to the Atlantic.  From these bases the U-boats where able to attack convoys much further west than before, which in turn forced the British escorts to extend their coverage. 


The Escorts

The key was to find the U-boat and at least prevent it from attacking the convoy and the tactics to accomplish this varied with the number and experience of the escorts assigned o the convoy.  Depending on the size of the escort force and the convoy, two or more escorts would sweep across the front of the convoy; one or more on each side, and at least one astern (see the attached diagram).  If weather permitted, one or more escorts would be detached from the screen to range far ahead or to the sides during the day as much as twenty miles from the convoy looking for ships that had either pulled ahead of the convoy (“rompers”) or lagged behind (“stragglers”).  Additional sweeps would be made in hopes of surprising a surfaced U-boat.  

Sonar was only means of detecting a submerged U-boat.  Once contact was made, the escort went to full speed for the attack.  Sonar could determine the range but not the depth and, as the escort approached, contact would be lost as she passed over the object.  To counter the lack of depth information, a pattern of depth-charges would be dropped set to explode at different depths.  Until the introduction of the forward-firing mouse-trap and, later the hedge-hog, nothing could be done by a single escort to avoid losing the contact at it passed over the target.  If there was the luxury of two escorts working a contact, one could feed range and bearing information to the second as the latter swept in for the attack.  No matter which approach was used, the exploding charges created a wall of bubbles that was impenetrable by sonar.  This complicated follow-up attacks.

Sometimes, when an escort got a doubtful contact, she would drop what were called “embarrassing” charges on the chance it was a U-boat and that the charges would either cause damage or at least keep it away from the convoy.  A depth-charge was lethal only for less than 100 feet.  Usually it was the accumulated pressure of several charges that would crack the U-boat’s pressure hull.

            If the U-boat was on the surface, gunfire and ramming were used to destroy her.  Ramming almost always disabled the escort but the trade-off was deemed worth it.

The British began equipping their escort with radar in 1941, but the sets weren’t reliable, had a limited range and, even in moderate seas a U-boat’s conning tower was too small a target to be detected.  Until a reliable radar set was developed, there was no way to detect a surfaced U-boat at night except by eye.  The best hope was to keep them far enough away during daylight so an attack could not be mounted at night. 

During a night attack, specially designed ammunition carrying magnesium flares attached to parachutes, know as star shells or snowflakes, were fired to illuminate the area and hopefully, a surfaced U-boat.  Often the only result was to give the U-boat better visibility for its attack.

Long-range aircraft were also employed to locate U-boats.  These planes flew from bases in Ireland, Iceland, and Newfoundland.  Equipped with depth-charges and, later, radar, they could spot and attack a surfaced target.  Also, the planes could alert an escort to the presence of a U-boat and help co-ordinate a surface attack.  Until early 1944 there was a large, mid-ocean gap that was beyond the range of aircraft patrols.  This “Black Hole” was the prime killing ground for the U-boats.  By the summer of 1944, small aircraft carriers and their screens of destroyer escorts were deployed as roving Hunter-Killer groups.  Instead of being tied to a single convoy, these groups were able either support a hard-pressed escort group or to track down individual U-boats.  By the time the carriers arrived in force, the bloodiest work had been done by surface escorts alone.

The U-boats

            German for submarine is unterseeboote and the name has been shortened simply to “U-boat”.  Since its introduction in World War I, the term has denoted only German submarines. 

            A U-boat on the surface at night was virtually invisible.  Keeping only its conning tower above water, it could get close to the flanks of a convoy or slip in between the columns without being detected.  Since sonar and ASDIC only worked if a U-boat was submerged and until the escorts had radar, the night surface torpedo attack was perfect.   To make the attacks more deadly, several U-boats would hit the convoy from different points in a coordinated action.  This was the Wolf-pack.

            The Wolf-pack concept (“die Rudeltakic”) was developed by Kapitän zur See (later Grossadmiral) Karl Dönitz in the late 1930s.  Through radio communications, Dönitz or his Operations officers coordinated the attacks of multiple U-boats against a convoy.  When information of a convoy was received at U-boat Headquarters [Befehlshaber der Unterseeboote (BdU)], messages were sent selected boats directing them to form a scouting line across the convoy’s projected track.  The boats were usually spaced twenty miles apart which is twice the normal visual range at sea so six boats could cover 120 miles.  The first one to locate the convoy would transmit a homing signal for the others and then continue to trail the convoy until the pack gathered.  When the pack was gathered, the attack began. 

            The favored position was on the dark side of the convoy with a moon illuminating the ships while leaving the U-boat in the shadows.   After the night's attacks, the boats would pull away to regroup, rest and send reports to Headquarters.  If contact with the convoy was maintained, they would surface out of visual range and trail behind or attempt to get ahead of the lumbering ships in order to gain a favorable position for the next night’s work.



            Knowing what your enemy plans to do and where his forces are is a crucial part of warfare.  There many ways of gathering this information, but three types formed the intelligence backbone for the Battle of the Atlantic.

            Probably the oldest why to get information is by using spies.  Both sides had agents who either passed along when convoys were leaving port or when a U-bout was about to go out on patrol.   Once ships began carrying radios, it became possible to locate them through radio direction finding (“RDF”).   This enables you to locate the target by plotting his radio transmissions by taking a bearing on the direction the signal is coming from.  If  multiple  locations can get a bearing on the enemy’s radio, you can get a fairly accurate fix.  The more bearings and/or the closer you are to the source the more accurate the location. 

            The third type of intelligence is crypto analysis; the ability to decode the enemy’s radio messages.  For most of the Battle of the Atlantic each side was reading the other’s coded signals.  However, in the fall of 1942, the Germans introduced more complex variation of their naval code which wasn’t broken by the Allies for several months during which the heaviest fighting occurred. 





Naval Bases

            There were four primary overseas naval bases the cutters used.  One lay in a beautiful green land; two others were wind-swept and bleak; and the fourth safe only after passing through a potentially lethal entrance.


Lisahally, Northern Ireland

            The town of Lisahally lies along the banks of Lough Foyle, three miles south of Londonderry.  Sailing up the River Foyle, bounded by gently rolling hills and dotted with small cottages, was a visual feast for the escorts’ weary men.  The base was well equipped to repair, resupply and rearm the battered ships.  It was a short tram ride to Londonderry’s pubs, restaurants, night clubs, churches and friendly people.  Other than the fact the beer was served warm, this was a most hospitable place to replenish the sailor’s soul.


Hvalfjordur, Iceland

            Just north of Reykjavik is Hvalfjordur (Whale Bay).  Surrounded on three sides by steep mountains, its mouth is exposed to the Atlantic Ocean.  In winter, winds roaring go from zero to a hundred knots in a heartbeat.  Winds strong enough to force an anchored ship onto the rocks and there were often accompanied by sleet that iced up equipment and cuts flesh like a knife.  This outpost was soon nicknamed “Valley Forge” by the Americans.  With only a Quonset Hut ashore for a bar and recreation center, there were no amenities to make a sailor desire to do anything but leave.  Except that leaving meant heading out to once more to the convoys and waiting U-boats.


Argentia, Newfoundland

            On the southwestern side of the Avalon Peninsula is Argentia, a deep harbor surrounded on three sides by sharp-edged mountains and on the fourth by a flat spit of land large enough to hold an airfield.  It is a bleak place in a bleakly beautiful land.  Leading to Argentia is Placentia Bay.  Coming in from the Atlantic, a mariner just has to follow the hundred fathom curve up the eastern side and then take a right when he sees the Mae West Peaks on the starboard bow.  The fathom curve is easy to follow during the day because on the right side the water is green and on the left a deep, mid-ocean blue.  But take care must be taken, because if Placentia Bay is missed in the fog, St Mary’s Bay just to the east also has the hundred fathom curve running north.

St. John’s, Newfoundland

            A slit cut by an ancient god in a solid wall of rock forms the entrance to this magnificent harbor.  Often shrouded by low lying fog, it is not an opening for the feint hearted but then, nothing in this land is.  Once through, the enclosed harbor opens to the left.  The north and east sides are bounded by cliffs while to the south and west the city sweeps upward to a range of mountains farther inland.  Packed with ships and sailors from around world, St. John’s felt like a town on the frontier of civilization.


            For the Allies and the European Axis partners (Germany and Italy) the Battle of the Atlantic was the longest single battle of World War II.  As noted in my Battle of the Atlantic Epigrams article, 696 U-boats and 25,870 men of their crews were lost.  More than 2,800 merchant ships, 175 warships, 1,777 aircraft and 33,000 Allied sailors and airmen died and an uncounted number of women and children were lost in the Atlantic from September 1939 to May 1945.

[1] Gainard, Joseph, Yankee Skipper,  Frederick A. Stokes and Company, New York, 1940

Web Site: Mike Walling

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