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The concept of amphibious assault ship is rather modern. This is a vessel from which troops are transported to the landing area by means of
helicopters, operated from a flight deck, or air-cushion vehicles, stored in an internal dock. But the landing of infantry troops to invade
a country is almost as ancient as human civilization is, and History tells about famous landings that changed the course of mankind. But
without doubt the most known amphibious operations took place during the 20th century: the disastrous assault in the Dardanelles during the
First World War, the successful landing in Alhucemas in 1925, or those performed in the Pacific and Normandy during the Second World War.
All of those landings had a common denominator: the troops arrived on their own feet and under enemy fire to the beaches where they had been
carried by means of barges, often paying a considerable price in lives. The landing in Inchon, during the Korean War, marked an inflection point
in this kind of operations, but it was during the Vietnam War, with the utilization of the helicopter, when the modern amphibious assault was
born. The new flying vehicle brought a radical change in the amphibious strategy and tactic, to which also contributed the availability of
modern air-cushion vehicles (ACV), the first truly amphibious vehicles in History.
Iwo Jima class
For the helicopter was the new means used in those operations, it was required to have ships specifically designed to operate with them. Already
during the 1960s the US Navy ordered the seven vessels that formed the Iwo Jima class, conceived to fulfill such mission, and previously it had
been experimenting with diverse aircraft carriers adapted to such mission. The leading ship USS Iwo Jima, commissioned in August 1961, was the first
ship retired from service, being scrapped in 1996. The USS Tripoli was turned into a missile trial launch platform and the rest of the ships were sunk as targets
between 2001 and 2010.
The ships of the Iwo Jima class had a flight deck with capacity for about 25 helicopters and two elevators in external position, but devoid of
catapults and arresting wires. These ships also lacked an internal dock to make use of landing craft. They had habitability for 2000 fully equipped
Marines and the 750 crewmen, and their cargo capacity included 24000 liters of fuel for vehicles, 1.5 millions of liters of JP-5 fuel for helicopters,
1060 cubic meters for diverse palletized cargo and 400 square meters for parking vehicles of any type.
These ships had an overall length of 188 meters, a maximum beam of 32 meters, a draught of 8.2 meters and a full-load displacement of 18500 tonnes.
The propulsion plant comprised two boilers Combustion Engineering, a single steam turbine Westinghouse and a single shaft, developing 23000 horsepower
and a top speed of 23 knots, while operational range is 10000 nautical miles at 20 knots.
The armament was variable for each ship, but in general comprised two/four 76-millimeter cannons in twin mountings, two octuple missile launchers
Sea Sparrow BPDMS, two Vulcan Phalanx CIWS mountings, four 25-millimeter chain cannons Bushmaster and four/eight 12.7-millimeter machine guns Browning.
Tarawa class
These were the largest amphibious assault ships ever built until being surpassed, even if by little, by those of the Wasp class. Initially nine
ships were intended to be built, but finally only five were completed due to the budget cuts following the end of the Vietnam War. They combine
in a single ship the prestations of the LPH (Landing Platform Helicopter), LPD (Landing Platform Dock), LCC (Amphibious Command Ship) and LKA
(Amphibious Cargo Ship), so they are denominated LHA (Landing Helicopter Assault), symbol designation for a general-purpose helicopter-carrier
amphibious assault ship.
These ships have a wide dock of 82 x 24 meters from which troops, vehicles and cargo are loaded into the landing barges or the ACV/LCAC (Air Cushion
Vehicle/Landing Craft Air Cushion). They have as well a large hangar of 250 x 24 meters, with a headroom of 6 meters, to transport the air wing
which is generally integrated by helicopters CH-46D/E Sea Knight and CH-53D Sea Stallion, but also STOVL aircraft AV-8B Harrier II, with a total
of 35 units which can be transferred to the flight deck via two elevators, one at larboard side, capable of 18 tonnes, and other astern,
capable of 36 tonnes.
The various internal decks are intercommunicated by cargo elevators capable of 1000 kilograms and ramps for troops and vehicles. There is cargo
capacity for more than 1900 fully equipped Marines, 3134 square meters for parking vehicles, 3311 cubic meters for palletized cargo, 38000 liters
of fuel for vehicles and 378,000 liters of JP-5 fuel for gas turbines. As landing craft they can transport, alternatively, up to four LCU
(Landing Craft Utility), two LCU and three LCM-8 (Landing Craft Mechanized), seventeen LCM-6 or forty-five LVTP-7 (Landing Vehicle Tracked Personnel)
and, due to diverse limitations in the internal distribution of the dock, only one LCAC.
There is also a wide sanitary area with three operating theaters and a hospital with 300 beds. For the role of command ship there is accommodation
for an adequate Naval Staff, as well as a wide CIC (Combat Information Center) in the isle, a criticized location for it is too exposed to missile
impacts.
These ships have an overall length of 254 meters, a maximum beam of 40.2 meters, a draught of 8.2 meters and a full-load displacement of 39967 tonnes.
The propulsion plant comprises two boilers Combustion Engineering, two steam turbines Westinghouse and two shafts, for a total output of 70000 horsepower
and a top speed of 24 knots, being operational range 10000 nautical miles at 20 knots.
The armament comprised, originally, three Mk 45 127-millimeter cannons in single mountings and two octuple missile launchers Sea Sparrow BPDMS.
These weapons were later removed and replaced by two Vulcan Phalanx CIWS mountings and two Mk 49 RAM (Rolling Airframe Missile) launchers.
Secondary armament comprises six 25-millimeter chain cannons Bushmaster and eight 12.7-millimeter machine guns Browning.
The five ships of the class were commissioned between May 1976 and May 1980. As 2016, the USS Tarawa, USS Nassau (ex Leyte Gulf) and USS Peleliu
(ex Da Nang, ex Khe Sanh) remain in the reserve, whereas the USS Saipan was scrapped in 2011 and the USS Belleau Wood (ex Philippine Sea) was sunk
as a target in 2006.
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