Mesopotamia Class (46-49) (FB)

## **Introduction**

Mesopotamia Class of Fast Battleships were the final generation of South American Union Navy (SAUN/SAFS) Fast Battleships restricted to the Washington and London Naval Treaty battleship be designed, constructed and completed before the outbreak of the 2nd World War. Could be arguably the 2nd best treaty battleship behind either American South Dakota Class or British KGV Class as the incorporated the lessons of the preceding Diamantina Class. Mesopotamia Class were assigned the hull numbers 46-49 which represent 46th or 49th battleships to constructed with the identification of FB which stands for Fast Battleship which started with World War 1 Legacy Dreadnoughts of the Occidental Class.

Majority of the Class saw service in 1942. Ships of the class are **S.A.F.S Mesopotamia FB-46**, **S.A.F.S Banda Oriental FB-47** , **S.A.F.S Mato Grosso FB-48** and **S.A.F.S Pontal FB-49**. With the first only being commissioned in late of August 1941 while the last being commissioned in early May 1942 main role of the Mesopotamia Class were 1. Tasked as an Powerful escort for the Aircraft Carrier Taskforces, 2. Hunt down any major enemy capital ships, 3. Provide surface bombardment to landing operations and 4. Flagship for Battleship Divisions or admiral staff when necessary.

**Ships in the Class**

* Mesopotamia FB-46
* Banda Oriental FB-47
* Mato Grosso FB-48
* Pontal FB-49

## **Armour Scheme**

The Citadel: One areas of improvement over the Diamantina Class is the improvement of the main armour scheme to be protected from 15 inch super heavy shell from a range of 25'000 to 30'000 meters or 25-30 kilometres. Which required an main belt of 15.1 Inches and deck of 8 Inches which was not possible under treaty regulations. Thus the South American Navy decided to use the same armour scheme which started with Chaco Austral Class but on a larger scale which was the form an armoured box around the magazines and machinery which equals to 8 inches which allowed lot of weight be saved the preceding class only had 7.1 inch armoured box around the magazines and machinery spaces while containing only 14.8 main belt but this entire armour scheme only be achieved at 47'500 Tons at normal load and 52,017 Tons at full load as well the deletion of the armoured conning tower and use an all or nothing armour scheme which results in decrease in weight to have thick armour around the places which could vulnerable from incoming shells and increasing a lot of weight in protecting the citadel.

Superstructure: This class follows the established practice of the current generation of South American treaty battleships having an 3 inch face on and 1.5 inch back on the CT or conning tower while rest of superstructure was given 1.5 inch of splinter protection.

Torpedo and underwater Protection: Torpedo defence on South American Treaty Fast Battleships depends on which class the Diamantina, Mesopotamia and Costa Rica Classes have torpedo defence which consist seven layers of depth with total depth around 6 meters. While Chaco Austral Class is around 5.5 Meters Deep which consist six layers of depth with total depth. The main belt dose extends down to waterline but it's last layer of the torpedo defence but the Armoured Box is last line if a torpedo managed to defeat the seven layers around the magazines and Machinery spaces but it's six layers not around those spaces. South American Torpedo Defence is made of series of liquid and non liquid filled void spaces. "South American Torpedo Defence dose not extend past turret 1 or 3 which turret 1 is A while 3 is X. The bulkhead thickness on all South American Treaty Battleships is 13.8 Inches."

Everywhere else: Every space or compartment that is not vital or not in the armoured citadel were only given splinter protection with the maximum thickness of 1.25.

Armament: The primary armament were protect by 17.1 face, 18 Barbette and 7inch side and roof. While the secondary armament are protected by 2 inch face and hoist while 1 inch everywhere else. The Anti-air armament are only protected by 1 inch face shield.

## Armament

**Artillery Armament**

* Primary: The primary firepower of the Class consist of 9 AMRJ 15/50 M1934 guns the same one used on Chaco Austral and Diamantina Classes  in 3 triple turrets with 2 forward with 1 super firing while other was aft of the superstructure. They are capable firing 2,300 pound 15inch super heavy shell at a maximum impact velocity of speed of 764 (m/s) at zero yards while lowest 470 (m/s) at 30,000 meters. The maximum elevation of the guns is +45° while lowest is -2. The gun are capable of firing a maximum of 2.1 rounds per minute. The 15inch super heavy shell was marvellous design as they good penetration capability with maximum penetration 821 millimetres at zero meters and 339.7 millimetres at 33,000 meters with maximum deck penetration of 288 millimetres at 33,000 meters. However it was very slow to reload compared to the traditional 15inch shell but had similar penetration of power of 16 or 18 traditional shells at the same range. It was also a problem that the shells were very large and heavy as it only 400 pounds less than American 16inch super heavy shell. "Major downside of the 2'300 Pound Shells were the inability to have any protective amount of armour at any range for the ship in question to fire the projectile."
* Secondary: The secondary armament consist of 10 x 2 AMJ 4.7/48 Model 1937 Dual Purpose Battery primarily located at amidships with 5 on each side with 2 elevated little bit higher the other 3 are placed amidships. Their shells are lighter then their 15inch counterparts with a maximum muzzle velocity of 500 metres per second and maximum impact velocity of 600 metres per second. They can fire a maximum of 16-20 rounds per minute. Their primarily use is against aircrafts and surface ships primarily smaller ships like destroyers and torpedo boats. They are supplied with 500 rounds per gun compared to 130 for the primary armament but their shells weigh at 54.37 pounds per round compared to 2,300 pounds per round for the 15inch super heavy shells. They are housed in twin turrets that is only protected by 2 inch face shield and barbette while 1 inch everywhere else. (Diamantina was only had 16 barrels largely due to treaty restrictions) The maximum celling for these guns were 39,400 Feet (12,000 Meters) the maximum range for 4.7/48 guns were little bit short of 14,000 meters or 14 kilometres.

**Anti-Air Suite**

* (Primary Defence): The Primary anti-Defence was the AMJ 4.7/48 Model 1937 Dual Purpose Battery primarily located at amidships with 5 on each side with 2 elevated little bit higher the other 3 are placed amidships. The maximum celling for these guns were 39,400 Feet (12,000 Meters).
* (Secondary Defence): The primary anti defence out side of the 4.7"/48 secondary battery were AIA 37/58 M1940 Medium Range AA Guns in 28 triple mounts. These were medium anti-air battery developed in 1940's from Avibrás Indústria Aeroespacial de or AIA they were designed to fire an 1.68 pound projectile at range of 22,000 feet at maximum elevation and 7 kilometres at minimum. The effective maximum range of the 37mm shells was actually less 7 kilometres and the maximum celling less than 9'000 feet due to the limited fire control instruments capability by 1941 and 1942 until by 1943 they were obsolete due to larger aircrafts entering service and lack of punch they were replaced in by less modern 40/60 Bofors guns at end of the Second War the Class in total carried 88 barrels in 22 quad mounts.
* (Close Anti-Air Defence):The secondary anti-air suite consisted of While containing 56 barrels of 20/70 Oerlikons in twin mounts evenly spread out across the hull for light aa defence. But unlike the 37mm they remained in service until up to the cold war where the replaced.

## **Simplified Specifications**

Dimensions

* Length: 798 feet Overall while 766.6 at the waterline
* Beam: 118.5 feet
* Draft: 35.8 feet and 38.30 at maximum

Displacement

* Light: 38,806 (Tons)
* Standard: 41,812 (Tons)
* Normal: 47,481 (Tons)
* Maximum: 52,017 (Tons)

Machinery

* Powerplant Output: 130,307 horsepower
* Speed: 29.5 Knots
* Range: 20,000 nautical miles

**Armour**

* Belt: 15.1 Inches "Inclined at 19 degrees"
* Primary Gun Turrets: "17.1 Inch Turret face, 18 Inch Barbette and 7 inch side and roof"
* Secondary Gun Turrets: "2 Inch Turret face, 2 Inch Barbette and 1 inch side and roof"
* Torpedo Bulkheads: 13.8 inches
* Deck: "8 Inches Armoured Box around the machinery and magazines while 1.25 Inch everywhere"
* Conning Tower: 3 inch face and 1.5 inch back
* Splinter Protection: 1.25 Inches

Armament

* (3 x 3) 9 AMRJ 15/50 M1934 Guns
* (10 x 2) AMJ 4.7/48 Model 1937 Dual Purpose Guns
* (28 x 3) AIA 37/58 M1940 Medium Range AA Batteries (Designed) but replaced by 1943
* (28 x 2) 20/70 Oerlikons Close Range AA Batteries (Designed)
* (22 x 4) 40/60 Bofors Medium Range AA Batteries (1943-1945)