Diamantina Class (FB) "42-45"

## Introduction

Diamantina Class was Series of SAUN/South American Navy Treaty Battleships laid down in early 1937 as revised Chaco Austral Class Battleship in the early 1936's. Diamantina Class was designed to provide more protection against the armour pricing shell they carried which was 2'300 pound shell from AMRJ 15in/50 Calibre Model 1934 gun. Diamantina would later to heavily inspire the Mesopotamia Class of Fast Battleships of the year 1938 design. Majority of the Class saw service in between 1940 and 1941 while S.A.F.S Diamantina herself saw service in 1940 in the North Atlantic and taking part in hunt for the Bismarck Class Battleship Bismarck along along with her sister ship S.A.F.S Panama FB-43. Ships of the class are S.A.F.S Diamantina FB-42, S.A.F.S Panama FB-43 , S.A.F.S Suriname FB-44 and S.A.F.S Tucuman FB-45. With the first only being commissioned in 14th of February 1940 while the last being commissioned in early August 1941 main role of the Diamantina 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**

* Diamantina FB-42
* Panama FB-43
* Suriname FB-44
* Tucuman FB-45

## Armour Scheme

* **The Citadel**: One areas of improvement over the Chaco Austral 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 14.8 Inches and deck of 7.1 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 6 inch armoured box around the magazines and machinery spaces while containing only 13.5 main belt but this entire armour scheme only be achieved at 43,429 Tons at normal load and shorting the ship to overall length of 660 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**: The Class have a bulkheads overall protection of 13.8 inches which was standard on every battleship that South American Union Navy (SAUN/SAFS) ever produced. The torpedo protection has depth of 6 meters and expands down to the triple bottom of the class which have void spaces filled with water while rest are filled with fuel.
* **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

Primary: The primary firepower of the Class consist of 9 AMRJ 15/50 M1934 guns the same one used on Chaco Austral Class 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 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 8 x 2 AMJ 4.7/48 Model 1937 Dual Purpose Battery primarily located at amidships with 4 on each side with 2 elevated little bit higher the other 2 are placed amidships. Their shells are lighter then their 15inch counterparts with a maximum muzzle velocity of 800 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. (Chaco Austral was only had 20 barrels but Diamantina Class 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 4 on each side with 2 elevated little bit higher the other 2 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 19 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 76 barrels in 19 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.

## Sensors and processing systems

### **Fire control**

* Diamantina Class Main Battery guns relay on two MBD-3 or Primary Battery Director Mark-3 which were 15-17 Feet tall fire control directors with positioned forward and aft of the class Superstructure. They are rated to achieve at least 50% accuracy between 20,000 and 30,000 yards which by South American Navy Doctrine is ideal battle engagement range for every battleship. But in reality it was less than 30,000 yards "21-22 Kilometres" as they had no accurate way to measure distance beyond that range but in early 1942 the MBD-3 directors had an SR-3F variant of the SR-3 Radar installed to assist in targeting of larger ships as well in assisting spot of shells and estimating range. The radar was also used for detecting enemy Warships.
* Diamantina Class also carried four SBD-5 or Secondary Battery Director Mark-5 to guide the Diamantina Class secondary gun armament which can be on dual purpose role against surface ships and aircrafts respectively. These director were mounted on the superstructure with 2 forward and aft while rest amidships on the portside and starboard and used a system of multiplexing receivers to track targets. But late 1942 the SBD-5 Directors had an SR-3J variant of the SR-3 Radar installed to assist in targeting of smaller and larger ships which made the director it self now guided by radar instead of optical sights. The SBD-5's were replaced by SBD-6 on post war ships which had better tracking abilities against Early Jets and late war aircrafts but they were not installed on the Diamantina Class.

### **Search Sensors**

* Diamantina Class radar sensors includes two SR-3C "Surface Search" and single AS-5H "Air Search" Radars. The SR-3C radars are mounted just bit aft of the bridge and aft the superstructure while the AS-5H radar is mounted high in the superstructure and the highest point of the Class. SR-3C Radar was developed in 1942 to track enemy Surface Ships while the AS-5H was designed to detect low and high flying aircrafts. SR-3C Radar had reliable detection range of 50 kilometres on Battleship or Aircraft sized vessel while Cruiser sized vessel only able be spotted at 40 kilometres but less than 30 kilometres for destroyers. While the AS-5H radar was developed in late 1941 to replace the early version of AS-5 radar which was variant A,B and C and has detection range of 150 kilometres for high flying bombers and around 30-40 for low flying aircrafts. But in late 1943 the AS-5H radar was replaced by the dual purpose DS-2A Radar which can be surface and aircraft search radar while the SR-3C was not fully replaced until mid 1944 by SR-7E which was similar but had have higher frequency and larger antenna. The SR-7E has detection range of 80 kilometres for surface vessels.

## Simple Specifications

**Dimensions**

* Length: 660 feet Overall while 628.60 at the waterline
* Beam: 118.5 feet
* Draft: 35.8 feet and 38.70 at maximum

**Displacement**

* Light: 34,935 (Tons)
* Standard: 37,724 (Tons)
* Normal: 43,429 (Tons)
* Maximum: 47,994 (Tons)

**Machinery**

* Powerplant Output: 135,944 horsepower
* Speed: 29.5 Knots
* Range: 20,000 nautical miles

**Armour**

* Belt: 14.8 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: "7.1 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
* (8 x 2) AMJ 4.7/48 Model 1937 Dual Purpose Guns
* (19 x 3) AIA 37/58 M1940 Cannons (Original) but replaced by 1943 by (19 x 4) 40/60 Bofors Cannons from (1943-1945)
* (28 x 2) 20/70 Oerlikons Autocannons (Original)

## History

### Early History

S.A.F.S Diamantina FB-42 was laid down at Alberto Daiber Shipyard in late 1938 joined by her sister-ship S.A.F.S Panama FB-43 at DIANCA Shipyards as a improvised and revised of pervious Chaco Austral Class with new armour scheme and new engines and propulsion system. Her sister-ships S.A.F.S Suriname FB-44 and S.A.F.S Tucuman FB-45 were laid down mid 1939. The Diamantina Class were quite similar and carried same guns as Chaco Austral Class. But was 30 feet shorter in overall length and 9.9 Feet wider in beam. This made them slightly better in overall handling and had a slightly better top speed. Only the first ships would be launched in early 1939 while the last ship was commissioned in early May 1941. With the commissioning of the Diamantina Class between late May 1941 and August 1941 which allowed the Chaco Austral Battleships to be reassigned to South American Pacific Fleet while Diamantina Class was assigned to the Atlantic Fleet as the Atlantic Fleet fast Battleship Wing while the Pacific had two fast Wings.

### Atlantic and North Africa Theatre

On the outbreak of war with the Axis Powers. Diamantina Class was quickly assigned as powerful deterrence against Axis Capital Ship Raiders, with S.A.F.S Diamantina FB-42 stationed with her Sister-ship S.A.F.S Tucuman FB-45 in Iceland while S.A.F.S Suriname FB-44 and S.A.F.S Panama FB-43 were stationed in Gibraltar. This was done if German Capital Ship Raider came from Iceland Greenland Gap which would cause the Battleships S.A.F.S Diamantina FB-42 and S.A.F.S Panama FB-43 to hunt down any German Capital Ship Raider that managed get passed the British Royal Navy or the Iceland and Greenland Gap. This plan was effective as British Royal Navy could worry less as South American Fast Battleships were in the Atlantic at any point and likely hood of German Capital raider breaking out drastically reduced. With War with Spain happen in mid July caused the Battleships S.A.F.S Diamantina FB-42 and S.A.F.S Panama FB-43 to be reassigned to Naval Base of Recife in state of Pernambuco. With the aftermath of the Battle of Denmark Strait the Battleships S.A.F.S Suriname FB-44 and S.A.F.S Panama FB-43 only be commissioned in late August 1941

The Battleship S.A.F.S Suriname FB-44 and S.A.F.S Panama FB-43 were assigned as the flagships of Operation Southern Cross which was an naval invasion of Spanish Colony of Southern Morocco under taskforce code named Allied Taskforce 54. But in August 12th 1941 the Fascist Spanish main fleet storied out to engage Allied Taskforce 54 which caused the heavy surface elements which includes The South American Fast Battleships S.A.F.S Suriname FB-44 and S.A.F.S Panama FB-43 along with their escorts to engage the Fascist Spanish fleet which ended in strategic victory for south American Navy in the battle of Santa Cruz De Tenerife where the old WW1 Dreadnoughts España, Alfonso XIII and Jaime I engaged by the Fast South American Battleships Suriname FB-44 and S.A.F.S Panama FB-43 as they attempt to intercept Allied Taskforce 54. In the 2.1 hour long gun fight the Battleships España, Alfonso XIII and Jaime I were sunk as well with bunch cruisers both light and heavy in exchange light losses on South American Side with consist mainly of destroyers. After the battle of Santa Cruz De Tenerife the Fascist Spanish never dared to challenge the landing operations in Spanish Colony of Southern Morocco. After landing operations of Operation Southern Cross had concluded Allied Taskforce 54 merged with allied fleet that was assigned to operation torch which was invasion of Western North Africa under taskforce code name Allied Force 55. But due to the threat of the Italian navy coming out all members of Class were assigned to the operation Torch. Nothing noteworthy had occurred as the Italian fleet never sailed out.

After the operation Torch and Southern Cross all south American Fast Battleships were reassigned to pacific Theatre but have to pass through the new modern Nicaragua canal built in late 1920's as they are unable fit through the dimensions of the Panama Canal. In order to avoid the dangerous trip through the Panama Canal the South American Fast Battleships were assigned to the North Atlantic theatre to protect the convoys of the time as they enter the canal. After the mission was done they were assigned to South American Navy's 1st fleet which was the major pacific fleet formation in the South Pacific.

### Pacific Theatre

Diamantina Class joined the Pacific theatre in late July 1942 after the Mesopotamia Class which was fully commissioned by that time replaced their role which allowed the Diamantina Class be transferred to the South American 1st Fleet which was operating in South Pacific in the vicinity of New Guinea. The Diamantina Class were tasked with providing support to the landing operations and escort South American Aircraft Carrier Taskforces in through out the Solomon Islands, New Guinea and New Britain Island. During the course of the Pacific war the Diamantina Class had to go through many shore bombardment operations and protect Aircraft Carriers during air-raids and attack by Imperial Japanese Army and Navy Air Forces. In early July 1943 Diamantina Class were tasked to bombard the coastal area of New Georgia as part of operation called Leopard's Vengeance which was a successful raid on the island of New Georgia which resulted in sinking the Japanese light cruiser and secured landing beaches New Georgia. On August 1943 the landing operation on Bougainville Island was supported by the South American Fast Battleships of 1st Fleet. Which caused Japanese counter response which was a naval bombardment and Aircraft Carrier Taskforces. What would be become 3rd Battle of Solomon Islands which consist of Units of South American 1st Fleet which is made of 10 Fleet Carriers, 9 Fast Battleships, 50 Cruisers and around 260 Destroyers against them were 2 Fleet Carriers, 5 Light Carriers, 11 Heavy Cruiser and 22 destroyers. The battle ended in South American Victory with both Shoukaku Class Carriers being sunk as well 3 Light Carriers and 1 Heavy Cruiser damaged. Diamantina Class was not part of the action as they were tasked to escort the Aircraft Carriers during the battle but they were credited destroying at least 30 Aircrafts during the battle.

The following month the Diamantina Class was sent to support the landing of Allied troops in Cape Gloucester in Papua New Guinea. During the operation the Diamantina Class took part in the second Battle of Cape Gloucester which was a failed attempt to capture the island of Wewak. During the battle the Diamantina Class along with their escorts were tasked to support the landings of South American and Australian troops which was followed by a fierce naval battle between the Diamantina Class along with their escorts and Japanese destroyers.. Which resulted with Single South American Destroyer being damaged and with the Japanese Destroyers being repelled with 3 being sunk. After the battle the 1st Fleet moved to Rabual to completely neutralize the base with heavy naval bombardment and shelling. After the destruction of the base the South American Fleet left the area for next operation. On November 1943 1st Fleet moved up the Admiralty Islands in New Britain as part of Operation Amazonia which was a major operation to seize the islands and build a airfield to completely neutralize Rabual from being used a naval or air base. As the 1st Fleet advanced to the islands the South American fleet encountered the Imperial Japanese Navy's Southern Force which was made of 1 Light Cruiser and 2 Destroyers. The battle ended in South American Victory with the taskforce sunk by Naval Carrier Aircrafts and the South American Fleet advancing into the islands with the Diamantina Class leading the way. On 25th of November the Admiralty Islands was officially occupied by the South American Marines with the help of South African units. On late December 1943 South American 1st Fleet moved up to Marshall and Caroline Islands to support USN Gilbert and Marshall Islands campaign. On January 1944 the 1st Fleet was involved in the third Battle of the Bismarck Archipelago which was a failed attempt to take Bismarck Archipelago from the Empire of Japan. The South American fleet was tasked to support the landings of the US Army in the northern part of the island and was to prevent any further reinforcement from arriving. The 1st Fleet participated in the battle with its escorts and took part in the battle of Tawitawi Atoll where the 1st Fleet lost 3 escorts while inflecting heavy losses on the Japanese which includes 500 Aircrafts shot to pieces and sinking the Japanese Aircraft Carrier Taihio. The 1st Fleet joined up with American Pacific fleet and continued the advance against the Japanese Empire. The 1st Fleet was assigned to support USN's Operation Musketeer I, II, and III which was liberation of the Philippines, Palau, and Philippines. The 1st Fleet took part in the battle of Leyte Gulf on October 20th 1944 which was the largest naval battle in the world. The 1st Fleet was assigned to support the amphibious landings of the southern part of the Leyte Gulf and took part in the naval battle which was the biggest naval battle in the Pacific Ocean.

South American Taskforce 32 which consist of the Fast Battleships S.A.F.S Diamantina FB-42, Panama FB-43, Mato Grosso FB-48 and Pontal FB-49 along with their escorts encountered the giant Japanese battleship Yamato near Samar Island. The Taskforce was ordered to attack the Japanese Battleship. the Battle was looks like it was one sided but the South American Navy held the advantage in weigh of firepower and speed as against them were two Kongo Class Battlecruisers, single Nagato Class battleship and the Giant Yamato. The South American Taskforce managed to sink the Haruna, Kong and Nagato but at cost the battleships Panama FB-43 and Mato Grosso FB-48 had severe damage but not damaged enough to be classified as sunk but the Yamato got badly hurt as well and would be later be sunk by combined air raid from South American and American Aircrafts. The South American 1st Fleet later moved up to Volcano and Ryūkyū Islands with their American allies support the landings of the western part of the islands where the 1st Fleet were constantly harassed by Japanese Kamikazes where the Diamantina Class played vital role of being floating anti-air batteries. After the war ended in 2 September 1945 the Diamantina Class were put in reserve fleet at Rio de Janeiro in August 1946. The class remain in the reserve fleet for 15 years until the early 1960's when Diamantina FB-42 was taken out of reserve fleet in put in mothball fleet in order to save money while Panama FB-43, Suriname FB-44 and Tucuman FB-45 were instantly sent to scrap yards as there were no need for them while the Costa Rica's Class Battleships were still around and it's until 1972 where Diamantina FB-42 was taken out of mothball fleet to be turned into museum ship in Recife by a organization called "The Friends of the Diamantina" where Diamantina remains to this very day.