There are many different types of ship, all designed for specific purposes and many with a long history of development behind them. This document attempts to detail the main types of vessel that were in existence in World War Two.

Merchant Vessels:

This section describes the various types of merchant vessel. These ships continued in their everyday tasks once war was declared, however all were exposed to the additional hazards of mines, torpedoes, air attack and surface attack without any meaningful protection of their own. Instead, they had to rely on others to protect them from harm. o8u21ub
The descriptions below of merchant ships are focussed on their design during the Second World War. Since then there has been a significant change in the arrangement of world shipping, with mass containerisation and massive bulk ore and oil carriers replacing the ships described below. Along with an increase in size has come a reduction in crew. It was not unusual to have a total compliment of 80 or more, whereas now it is not unusual to have a total compliment of about 25. Improved designs (with respect to both safety and cargo carrying capacity) have generally removed the central navigation bridge, and the aircraft has all but eliminated the passenger liner.

1. Tanker:
A tanker can be defined as: “A merchant ship, designed for the specific purpose of transporting liquid cargoes in bulk.”
Tankers generally have their machinery spaces aft (at the stern, or back end, of the ship). Forward of this are the cargo tanks. These are numbered from forward to aft, with the number one tank being the furthest forward. Each tank is further divided longitudinally (from fore to aft) by one or more oil-tight bulkheads, so the vessel may have an arrangement such as port number one tank, starboard number one tank, and (perhaps) centre number one tank. This improves stability by preventing liquid sloshing from side to side when the vessel rolls. One or more pump rooms would be provided, and these are used for discharging cargo.
Tanks can be fitted with heating systems (to allow heating of heavy oils to enable them to flow), steam smothering systems (to put out a fire in the tank) and vents (to allow gas to escape). These vents would be fitted with flame arrestors on vessels where light oil cargoes were intended to be carried. At around the mid point of the ship would be the main superstructure, containing accommodation for deck officers, the navigation bridge and the radio room. The accommodation for the engineers would be at the stern, above the engine room.
During the Second World War, tankers were particularly valuable targets. Whilst the loss of general cargo vessels caused much concern, it was the loss of tankers that caused the most anxiety as they were being lost at a much greater rate. As the highest-value ships in a convoy, tankers were normally placed in the inner columns. This shielded them somewhat from attack, although the losses continued to be a problem until the Battle of the Atlantic was finally decided.
Tankers are difficult ships to sink. They are well subdivided in to watertight compartments, and are designed to carry a liquid of approximately the same density as water. If you put a hole in the starboard (right) side of the tanker, the oil will run out and the vessel will list (lean) to port (the left) whilst rising slightly out of the water as the weight of cargo is reduced. The vessel will only sink if structural failure occurs.
The main danger faced by crews of tankers was fire. Whilst crude oil is difficult to set alight (it is thick, often does not flow unless it is heated, and if a lighted match is dropped in to it the match will simply go out), refined products (such as petrol and aviation fuel) can be very flammable.

2. Passenger Liner:
A passenger liner may be defined as: “A merchant vessel designed for the main purpose of carrying passengers.”
Passenger liners are usually fast ships, with a speed between 25 and 30 knots. Passenger liners were very different ships from the cruise liners of today. Their main purpose was to transport people between destinations, in much the same way as the airliner does today, rather than to provide a pleasant holiday experience. In the same manner as a modern airliner, passengers were split in to a number of classes. The first class passengers travelled in luxury, whilst the lowest class passengers were packed in as densely as possible.
The most important aspect of a passenger liner was its speed, with faster ships attracting more passengers and higher prices. This was because passengers simply wanted to get to their destination rather than enjoy the process of travelling. This obsession with speed fuelled great rivalry between the great liner companies, particularly on the prestigious North Atlantic route where the Blue Riband trophy was handed to the fastest ship to make the crossing.
The speed of this ships was a great advantage during the Second World War, as it made them almost invulnerable to submarine attack. As they could easily outpace even a surfaced submarine, they could be torpedoed only if the ship accidentally sailed in to range of the submarine. As the torpedo range was limited, the ocean very big and submarines reasonably few in number, passenger liners were unlikely to be attacked even if unescorted.
Passenger liners were essential to moving the large quantities of troops needed around the world. One of the largest ships was the RMS Queen Mary, which carried up to 15,000 troops per trip, and their presence simplified the vast logistical problem facing the Allies. Germany and Italy had less need for such vessels, particularly as their sea lanes were generally less secure than the Allies and the fighting was generally reachable by land, although if they had managed to take Europe as planned they would have been essential to any next steps and their lack was keenly felt in the Norwegian campaign. Japan’s problems were more complex. Passenger liners would have made their expansion much easier, however once they began retreating their shipping was not safe and such ships would not have helped. Passenger liners were very vulnerable to surface and air attack and, in areas where such threats were present, needed to be heavily escorted. Submarines, however, posed little threat and liners could operate in waters known to contain submarines provided they had a choice of routes (i.e. were not constrained to going through a particular area).
3. Bulk carrier:
A bulk carrier may be defined as: “A merchant vessel designed for the primary purpose of carrying solid cargo in bulk.”
These vessels were developed from a need to be able to handle certain types of cargo more efficiently then could be done in standard general cargo vessels. This included goods such as grain (which could be piped in and out of holds quickly), coal and iron ore (which were easier to handle in bulk rather than bagged on pallets).
Bulk carriers could be extremely vulnerable to submarine attack if they carried very dense cargoes, such as iron ore, scrap metal etc. Such dense cargoes mean that holds contain a lot of empty space to provide the necessary buoyancy. If the ship is torpedoed, water rushes in to the empty space, rapidly destroying the ship’s reserve of buoyancy and often causing structural failure. It was not unusual for scrap metal or iron ore carriers to sink within two minutes of being torpedoed, and they were not popular assignments for merchant crews because of this.
4. General Cargo Vessel:

A general cargo vessel may be defined as: “A merchant vessel designed for the primary purpose of carrying break-bulk dry cargo.”
These ships generally had a central engine room, with cargo holds forward and aft of this. The accommodation and navigating bridge was located above the engine room. Accommodation could also be provided at the stern of the vessel (in the poop) and at the bows (in the forecastle). These ships generally had their own cargo-handling equipment (booms) so that they could handle cargo without having to rely on shore facilities. During the Second World War, guns were fitted for defensive purposes. The speed of these vessels varied considerably, from only five or six knots for old tramp steamers up to over 15 knots for fast cargo liners.
Although a rare sight nowadays, the general cargo vessel has a long history, stretching back for as long as cargo was carried by sea. This type of vessel usually carries cargo stowed on pallets, lifted in and out of the hold by cranes and stowed within the hold by the ship’s crew. Cargo handling operations were labour-intensive, and it was for this reason that large crews were carried.
These vessels carried almost everything that was required to be shipped (from bags of flour to ammunition and military vehicles). Containerisation (with all its efficiency improvements) has resulted in this type of vessel being almost eliminated in the modern world.
In the days immediately before the Second World War there were many different shipping lines, and the lines that ships belonged to were easily recognisable by the distinctive paint schemes and funnel markings. The outbreak of war brought this flourish of colour to an end, with ships being painted a uniform drab grey.
Merchant shipping is very vulnerable to attack, although a determined defence sometimes made an attacker withdraw.
5.Wartime Emergency Vessels
Wartime emergency vessels were built by Britain, Canada and the United States of America.
They can be defined as: “Merchant vessels falling in to the category of: Empire ships; Liberty ships; Victory ships; ‘Oceans’, ‘Forts’ and ‘Parks’; T1, T2 and T3 tankers.”
The wartime emergency designs are vessels mass-produced under emergency programmes in Britain, Canada and the United States of America. They include almost every type of ocean-going merchant ship.
Having filled her large shipyards with warships, Britain had a pressing need to find new merchant tonnage to offset the losses of those being sunk. Ships were built wherever there was space in British territories, with those built in Britain bearing the prefix ‘Empire’ and known as ‘Empire’ ships, whilst those built in Canada bore the prefix ‘Fort’ or the suffix ‘Park’.
The Empire ships were a wide variety of different types. Each shipyard was tasked with building the vessels that they could build most efficiently, resulting in a very mixed bag of ships but having the advantage that work could begin immediately, with the existing skill base, in existing yards, and without any special provisions being required for their construction. One ship type, devised by the J L Thompson & Sons yard, had been specifically modified for mass production. This was based on a pre-war design for the Dorington Court, and resulted in a general cargo ship of around 10,000 tons deadweight and a speed of 11 knots. The first wartime ship of this type was the Empire Liberty, launched on the 28th August 1941.
Desperate for even more new tonnage, in late 1940 British representatives (including one from the Thompson yard) took the Empire Liberty plans to America to try to persuade the American government to let Britain place orders for 60 new ships. The Americans agreed, however no space existed in shipyards to allow them to be built and it was decided to build two new shipyards to meet the British need. These ships bore the prefix ‘Ocean’, with the first ship (the Ocean Vanguard) being launched on 15th October 1941.
The first vessels built in Canada (the ‘Forts’) were closer to the Dorington Court plans, and were known as the ‘North Sands’ type (after the J L Thompson & Sons yard). Improvements in machinery produced the ‘Victory’ ship (which was very different to the US ‘Victory’ ship), and further machinery changes resulted in the ‘Canadian’ ship.
The ‘Parks’ were built in Canada by the Park Steamship Company Ltd. The majority were ‘North Sands’, ‘Victory’ or ‘Canadian’ type, identical to the ‘Forts’, however some bulk cargo and tanker vessels were also built. Other merchant ships were also mass produced in Canada, including repair ships, coasters and tugs.
Simultaneous with the decision to build ships for the British was a decision to rapidly expand the US merchant fleet, however the choice of a design appropriate for mass production was a difficult one. The previous ships built by the US Maritime Commission were of a very high quality (but not suited to mass production), in stark contrast to the British wartime designs (which deliberately emphasised speed of construction), and there was considerable resistance to the idea of lowering standards to build ships rapidly. Faced however, with an urgent need, little time and a sound and readily available design a common-sense decision was taken to adopt the basic British concept for the American emergency fleet. This design was modified somewhat to further aid mass production and to suit American building techniques and other US preferences, and orders were placed for the first 200 of these ships in early 1941.
As with the ‘Ocean’ ships, no shipyards existed to build these vessels and a total of nine new shipyards were announced (including the two required to build the British vessels). Later expansions resulted in even more shipyards, and a total completed fleet of 2,710 ships.
Whilst the Liberty ship programme was in its early stages it was recognised that there was a need to provide higher quality vessels to meet post-war requirements. This led to the design of the ‘Victory’ ship, which was faster than the Liberty ship, with improved seakeeping abilities, better machinery and more modern cargo handling gear.
Along with the programme to build general cargo vessels (the Liberty and Victory ships) there was also a requirement to build new tankers, to replace losses, meet anticipated new demand and provide a post-war tanker fleet. These ships were a mix of mass-produced and individually designed vessels, some being built in yards originally intended for Liberty ship production and some being built privately.
After the war, many of these ‘emergency’ vessels deteriorated rapidly (particularly the Liberty and North Sands vessels). One post-war mariner summed up the attitude amongst seafarers when he said “you knew your career was over when they assigned you to a Liberty ship”. Nevertheless, all these vessels fulfilled a vital need. They quickly provided essential cargo capacity, to an adequate standard and (generally) without major flaws.
Generally the emergency ships can be regarded as normal merchant vessels, however concessions made to aid rapid production often made the ships less pleasant to sail on, uglier and less than ideal in many small ways.