Defensively Equipped Merchant Ships
Encyclopedia
Defensively Equipped Merchant Ship (DEMS) was an Admiralty
Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...

 Trade Division program established in June, 1939, to arm 5,500 British merchant ships with an adequate defence against enemy submarines and aircraft. The acronym DEMS was used to describe the ships carrying the guns, the guns aboard the ships, the military personnel manning the guns, and the shore establishment
Stone frigate
Stone frigate is a nickname for a naval establishment on land. The term has its origin in Britain's Royal Navy after its use of Diamond Rock, off Martinique, as a 'sloop of war' to harass the French...

 supporting the system.

Background

In the eighteenth and nineteenth centuries, European countries such as Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 Holland and Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

 armed their merchant ships to prevent capture by pirates
Piracy
Piracy is an act of robbery or criminal violence at sea. The term can include acts committed on land, in the air, or in other major bodies of water or on a shore. It does not normally include crimes committed against persons traveling on the same vessel as the perpetrator...

, enemy commerce raiders and privateer
Privateer
A privateer is a private person or ship authorized by a government by letters of marque to attack foreign shipping during wartime. Privateering was a way of mobilizing armed ships and sailors without having to spend public money or commit naval officers...

s when they conducted overseas trade. The most heavily armed were ships carrying valuable cargo back from the Far East
Far East
The Far East is an English term mostly describing East Asia and Southeast Asia, with South Asia sometimes also included for economic and cultural reasons.The term came into use in European geopolitical discourse in the 19th century,...

. For example, the East Indiamen
East Indiamen
An East Indiaman was a ship operating under charter or license to any of the East India Companies of the major European trading powers of the 17th through the 19th centuries...

 class of ships were constructed from the ground up with defence in mind, with their heavy armament making them equivalent to naval ships of the line
Ship of the line
A ship of the line was a type of naval warship constructed from the 17th through the mid-19th century to take part in the naval tactic known as the line of battle, in which two columns of opposing warships would manoeuvre to bring the greatest weight of broadside guns to bear...

. Once the threat passed after the end of the Napoleonic Wars
Napoleonic Wars
The Napoleonic Wars were a series of wars declared against Napoleon's French Empire by opposing coalitions that ran from 1803 to 1815. As a continuation of the wars sparked by the French Revolution of 1789, they revolutionised European armies and played out on an unprecedented scale, mainly due to...

 in 1815, armed merchant ships like East Indiamen were replaced with faster and lighter unarmed ships such as clipper
Clipper
A clipper was a very fast sailing ship of the 19th century that had three or more masts and a square rig. They were generally narrow for their length, could carry limited bulk freight, small by later 19th century standards, and had a large total sail area...

s.

World War I

During the First World War
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, Britain
British Empire
The British Empire comprised the dominions, colonies, protectorates, mandates and other territories ruled or administered by the United Kingdom. It originated with the overseas colonies and trading posts established by England in the late 16th and early 17th centuries. At its height, it was the...

 armed its merchant ships to help defend them against U-boats. A single stern gun, equivalent to what a submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

 might carry, was mounted; and civilian captains were encouraged to flee and shoot back from their more stable gun platform. 766 civilian ships had been armed by December, 1915. Arming of merchant ships gave Germany an excuse for moving toward unrestricted submarine warfare
Unrestricted submarine warfare
Unrestricted submarine warfare is a type of naval warfare in which submarines sink merchantmen without warning, as opposed to attacks per prize rules...

.

The first merchant ship lost to U-boats was an 866-ton British steamer outbound from Grangemouth
Grangemouth
Grangemouth is a town and former burgh in the council area of Falkirk, Scotland. The town lies in the Forth Valley, on the banks of the Firth of Forth, east of Falkirk, west of Bo'ness and south-east of Stirling. Grangemouth had a resident population of 17,906 according to the 2001...

 to Stavanger
Stavanger
Stavanger is a city and municipality in the county of Rogaland, Norway.Stavanger municipality has a population of 126,469. There are 197,852 people living in the Stavanger conurbation, making Stavanger the fourth largest city, but the third largest urban area, in Norway...

 with a cargo of coal, iron plate, and oil. was stopped by U-17 on 20 October 1914; and a boarding party
Boarding (attack)
Boarding, in its simplest sense, refers to the insertion on to a ship's deck of individuals. However, when it is classified as an attack, in most contexts, it refers to the forcible insertion of personnel that are not members of the crew by another party without the consent of the captain or crew...

 gave Glitra's crew time to disembark into lifeboats
Lifeboat (shipboard)
A lifeboat is a small, rigid or inflatable watercraft carried for emergency evacuation in the event of a disaster aboard ship. In the military, a lifeboat may be referred to as a whaleboat, dinghy, or gig. The ship's tenders of cruise ships often double as lifeboats. Recreational sailors sometimes...

 before sinking the ship by opening valves to flood holds with seawater. The procedure followed customs originated by surface ships. International maritime law required the naval vessel to make adequate provisions for the safety of the merchant crew and passengers before sinking their ship.

Imperial Germany focused use of U-boats against merchant shipping in response to British blockade of German merchant shipping by declaring the entire North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

 a war zone on 2 November 1914. On 5 February 1915 Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 published notice declaring a war zone in all waters around Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

 and Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

. Within that zone, Germany conducted unrestricted submarine warfare
Unrestricted submarine warfare
Unrestricted submarine warfare is a type of naval warfare in which submarines sink merchantmen without warning, as opposed to attacks per prize rules...

 against merchant ships from 18 February 1915 without warning and without regard to safety of their crew.

U-boats still conformed to earlier conventions of stopping ships when possible, but the typical submarine mounted only a single gun. The two procedures for sinking merchant ships were compared in 1915. Merchant ships escaped 42% of torpedo
Torpedo
The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...

 attacks made without warning, in comparison to 54% escaping from conventional surface attempts to stop the ship. Guns aided escape and approximately one submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

 per month was sunk (most by Q-ships) while attempting a surfaced stop.

The number of civilian merchant ships armed with anti-submarine guns rose to 1,749 by September 1916 and 2,899 by February 1917. The United States responded to unrestricted submarine warfare
Unrestricted submarine warfare
Unrestricted submarine warfare is a type of naval warfare in which submarines sink merchantmen without warning, as opposed to attacks per prize rules...

 by severing diplomatic relations
Diplomacy
Diplomacy is the art and practice of conducting negotiations between representatives of groups or states...

 with Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 on 3 February 1917. A filibuster
Filibuster
A filibuster is a type of parliamentary procedure. Specifically, it is the right of an individual to extend debate, allowing a lone member to delay or entirely prevent a vote on a given proposal...

 in the United States Senate
United States Senate
The United States Senate is the upper house of the bicameral legislature of the United States, and together with the United States House of Representatives comprises the United States Congress. The composition and powers of the Senate are established in Article One of the U.S. Constitution. Each...

 temporarily delayed President Woodrow Wilson
Woodrow Wilson
Thomas Woodrow Wilson was the 28th President of the United States, from 1913 to 1921. A leader of the Progressive Movement, he served as President of Princeton University from 1902 to 1910, and then as the Governor of New Jersey from 1911 to 1913...

's proposal on 26 February 1917 to arm United States merchant ships, but arming started in March under an executive order.

World War II

Old naval guns had been stored since 1918 in major seaports for possible use during future hostilities. During the Second World War, the objective was to equip each ship with a low-angle gun mounted aft as defence against surfaced submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s and a high-angle gun and rifle-calibre machine gun
Machine gun
A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

s for defence against air attack. 3,400 ships had been armed by the end of 1940; and all ships were armed by 1943.

The low-angle guns were typically in the 3-inch to 6-inch range (75–150 mm) depending on the size of the ship. Rifle
Rifle
A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...

-caliber machine guns were augmented or replaced by 20 mm Oerlikon
Oerlikon 20 mm cannon
The Oerlikon 20 mm cannon is a series of autocannons, based on an original design by Reinhold Becker of Germany, very early in World War I, and widely produced by Oerlikon Contraves and others...

 as they became available. The High-Angle QF 12pdr Mk V mount
QF 12 pounder 12 cwt naval gun
The QF 12 pounder 12 cwt gun was a common calibre naval gun introduced in 1894 and used until the middle of the 20th century. It was produced by Armstrong Whitworth, Elswick and used on Royal Navy warships, and exported to allied countries...

 was the most common anti-aircraft gun, and later ships sometimes received 40 mm Bofors guns
Bofors 40 mm gun
The Bofors 40 mm gun is an anti-aircraft autocannon designed by the Swedish defence firm of Bofors Defence...

.

Untrained gunners posed significant risk to friendly aircraft in the absence of efficient communications. DEMS guns were manned by 24,000 Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 personnel and 14,000 men of the Royal Artillery
Royal Artillery
The Royal Regiment of Artillery, commonly referred to as the Royal Artillery , is the artillery arm of the British Army. Despite its name, it comprises a number of regiments.-History:...

 Maritime Regiment. 150,000 merchant sailors were trained to assist by passing ammunition
Ammunition
Ammunition is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions...

, loading, and replacing casualties among the military gun crew. Initially, Royal Artillery personnel provided anti-aircraft protection by bringing their own machine-guns aboard ships operating close to the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...

. DEMS gunners were often retired military personnel and young "Hostilities Only" ratings commanded by a petty officer
Petty Officer
A petty officer is a non-commissioned officer in many navies and is given the NATO rank denotion OR-6. They are equal in rank to sergeant, British Army and Royal Air Force. A Petty Officer is superior in rank to Leading Rate and subordinate to Chief Petty Officer, in the case of the British Armed...

 or Royal Marine sergeant
Sergeant
Sergeant is a rank used in some form by most militaries, police forces, and other uniformed organizations around the world. Its origins are the Latin serviens, "one who serves", through the French term Sergent....

. Large ships sometimes embarked a junior naval officer to command the DEMS gunners.

Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 placed guns on 713 ships.

D-day landings and the Royal Observer Corps

In 1944, during preparations for the invasion of France called Operation Overlord
Operation Overlord
Operation Overlord was the code name for the Battle of Normandy, the operation that launched the invasion of German-occupied western Europe during World War II by Allied forces. The operation commenced on 6 June 1944 with the Normandy landings...

 there was deep concern over the danger to Allied aircraft from the large number of DEMS involved in the landings. A request for volunteer aircraft recognition experts from the Royal Observer Corps
Royal Observer Corps
The Royal Observer Corps was a civil defence organisation operating in the United Kingdom between 29 October 1925 and 31 December 1995, when the Corps' civilian volunteers were stood down....

 produced 1,094 highly qualified candidates, from which 796 were selected to perform valuable aircraft recognition duties as seaborne volunteers.

These Seaborne Observers were organised by Group Commandant C.G.Cooke and trained at the Royal Bath Hotel Bournemouth
Bournemouth
Bournemouth is a large coastal resort town in the ceremonial county of Dorset, England. According to the 2001 Census the town has a population of 163,444, making it the largest settlement in Dorset. It is also the largest settlement between Southampton and Plymouth...

 before the volunteers temporarily joined the Royal Navy with the rank of Petty Officer (Aircraft Identifier). The volunteers continued to wear their ROC uniforms, but wore SEABORNE shoulder flashes and a Royal Navy brassard with the letters RN. During the D-day landings
D-Day
D-Day is a term often used in military parlance to denote the day on which a combat attack or operation is to be initiated. "D-Day" often represents a variable, designating the day upon which some significant event will occur or has occurred; see Military designation of days and hours for similar...

 two Seaborne observers were allocated to each of the Defensively Equipped Merchant Ships, both British and American vessels. The ROC volunteers were given direct control of each ship's anti aircraft batteries, immediately reducing the previously high level of friendly fire
Friendly fire
Friendly fire is inadvertent firing towards one's own or otherwise friendly forces while attempting to engage enemy forces, particularly where this results in injury or death. A death resulting from a negligent discharge is not considered friendly fire...

, or collateral damage
Collateral damage
Collateral damage is damage to people or property that is unintended or incidental to the intended outcome. The phrase is prevalently used as an euphemism for civilian casualties of a military action.-Etymology:...

incidents as they are now known. Their success is measured by a signal from Wing Commander P.B. Lucas, Air Staff Officer who reported:
"The general impression amongst the Spitfire wings, covering our land and naval forces over and off the beach-head, appears to be that in the majority of cases the fire has come from warships and not from the merchant ships. Indeed I personally have yet to hear a single pilot report that a merchant vessel had opened fire on him"


Twenty two Seaborne observers survived their ships being sunk, two lost their lives and several more were injured during the landings. The Seaborne operation was an unqualified success and in recognition, His Majesty King George Vl
George VI of the United Kingdom
George VI was King of the United Kingdom and the Dominions of the British Commonwealth from 11 December 1936 until his death...

 approved the wearing of the SEABORNE flash as a permanent feature of the uniform. In addition, ten Seaborne members were mentioned in despatches. After the invasion and just before his death Air Chief Marshal Trafford Leigh-Mallory
Trafford Leigh-Mallory
Air Chief Marshal Sir Trafford Leigh-Mallory KCB, DSO & Bar was a senior commander in the Royal Air Force. Leigh-Mallory served as a Royal Flying Corps pilot and squadron commander during World War I...

 wrote the following to be circulated to all ROC personnel:
"I have read reports from both pilots and naval officers regarding the Seaborne volunteers on board merchant vessels during recent operations. All reports agree that the Seaborne volunteers have more than fulfilled their duties and have undoubtedly saved many of our aircraft from being engaged by our ships guns. I should be grateful if you would please convey to all ranks of the Royal Observer Corps, and in particular to the Seaborne observers themselves, how grateful I, and all pilots in the Allied Expeditionary Air Force, are for their assistance, which has contributed in no small measure to the safety of our own aircraft, and also to the efficient protection of the ships at sea.

The work of the Royal Observer Corps is quite often unjustly overlooked, and receives little recognition, and I therefore wish that the service they rendered on this occasion be as widely advertised as possible, and all units of the Air Defence of Great Britain are therefore to be informed of the success of this latest venture of the Royal Observer Corps."


As of 2010 there is a Seaborne Observers’ Association for the dwindling number of survivors. Ex-Air Vice-Marshal George Black
George Black (RAF officer)
Air Vice-Marshal George Phillip Black CB OBE AFC RAF was a British Royal Air Force pilot, a senior Royal Air Force officer in the 1970s and 1980s and a Commandant Royal Observer Corps. From 1971 to 1973, Black was Station Commander of RAF Wildenrath in West Germany.-Early years:In 1950 Black left...

, a former Commandant ROC, is the honorary president.

United States

The Merchant Marine Act of 1936
Merchant Marine Act of 1936
The Merchant Marine Act of 1936 is a United States federal law. Its purpose is "to further the development and maintenance of an adequate and well-balanced American merchant marine, to promote the commerce of the United States, to aid in the national defense, to repeal certain former legislation,...

 identified mariners aboard United States flagged merchant ships as military personnel in time of war. Neutrality Acts prevented arming of United States flagged merchant ships until 17 November 1941, although American-owned ships under Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...

nian registry had been armed earlier. Guns were manned by United States Navy Armed Guard
United States Navy Armed Guard
United States Navy Armed Guard units were established during World War I in an attempt to provide defensive firepower to merchant ships in convoy or merchant ships traveling alone...

. United States began equipping ships of other nations with guns and United States Navy Armed Guard
United States Navy Armed Guard
United States Navy Armed Guard units were established during World War I in an attempt to provide defensive firepower to merchant ships in convoy or merchant ships traveling alone...

 on 24 January 1942. United States policy was stated by the Vice Chief of Naval Operations
Chief of Naval Operations
The Chief of Naval Operations is a statutory office held by a four-star admiral in the United States Navy, and is the most senior uniformed officer assigned to serve in the Department of the Navy. The office is a military adviser and deputy to the Secretary of the Navy...

 on 19 August 1942: "Ships sailing independently should be armed. Ships sailing in regularly made-up convoys, other than ships bound to North Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 or tankers
Tanker (ship)
A tanker is a ship designed to transport liquids in bulk. Major types of tankship include the oil tanker, the chemical tanker, and the liquefied natural gas carrier.-Background:...

 en route to the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, may sail unarmed if the urgency of delivery of their cargo warrants it."

The United States followed the British practice of a single large gun aft. Early United States installations included low-angle 4"/50 calibre guns (Mark 9) removed from old Wickes
Wickes class destroyer
The Wickes-class destroyers were a group of 111 destroyers built by the United States Navy in 1917-1919. Along with the 6 preceding Caldwell class and 155 subsequent Clemson-class destroyers, they formed the "flush-deck" or "four-stack" class. Only a few were completed in time to serve in World...

 and Clemson class
Clemson class destroyer
The Clemson class was a series of 156 destroyers which served with the United States Navy from after World War I through World War II.The Clemson-class ships were commissioned by the United States Navy from 1919 to 1922, built by Newport News Shipbuilding & Dry Dock Company, New York Shipbuilding...

 destroyers. The first installations of dual-purpose 5"/38 calibre guns began in September, 1942, on new ships over 10,000 tons. Victory ship
Victory ship
The Victory ship was a type of cargo ship produced in large numbers by North American shipyards during World War II to replace shipping losses caused by German submarines...

s carried a 3-inch gun on the bow, 20 mm machine gun tubs port and starboard between the first and second holds; a second pair of 20 mm guns on the bridge wings
Bridge (ship)
The bridge of a ship is the room or platform from which the ship can be commanded. When a ship is underway the bridge is manned by an OOW aided usually by an AB acting as lookout...

, a third pair on the after edge of the superstructure
Superstructure
A superstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such as buildings, bridges, or ships...

, and a fourth pair between the after (Number 5) hatch and the 5"/38 calibre gun on the stern
Stern
The stern is the rear or aft-most part of a ship or boat, technically defined as the area built up over the sternpost, extending upwards from the counter rail to the taffrail. The stern lies opposite of the bow, the foremost part of a ship. Originally, the term only referred to the aft port section...

.
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