American Cold War Amphibious Ships Part II (1960-1975)

This is the continuation of my overview of American amphibious warfare ships of the Cold War. Part I, which covered 1950-1960, can be found here.

As mentioned in the previous part, 1960 marked an inflection point for the amphibious fleet. First, the slow decline in numbers that had begun with the end of the Korean war was halted and the fleet entered several years of rapid growth. Second, new types of large amphibious ships were beginning to be introduced, marking the end of the WWII fleet architecture that had relied on converted cargo ships.

The most important of these new ships were the purpose-built Amphibious Assault Ships (LPH). Three WWII-era carriers had been converted to interim LPH's during the late 1950's, and a fourth - USS Valley Forge (LPH-8) - joined the fleet in 1961. However, these conversions were rather austere and only intended as stopgaps until a purpose-built ship could be designed. This took the form of USS Iwo Jima (LPH-2), a truly revolutionary vessel and the lead ship in a class of six. At 180 meters in length, she was capable of accommodating 22 helicopters, 1,750 troops, 12,500 square feet of vehicles, and 50,000 cubic feet of cargo. The design airwing consisted of 20 HUS and 2 HR2S helicopters. Compared to the old Attack Transports (APA) that the LPH effectively replaced, this was slightly more men but less than half the cargo volume. This reduction in materiel was the result of a new approach to amphibious warfare that emphasized light airmobile forces.

USS Guadalcanal (LPH-7), the third member of the Iwo Jima-class, with a airgroup of HUS helicopters.

Thus, the Iwo Jima-class effectively replaced the 10 knot LCVP with the 80 knot HUS Seahorse (redesignated UH-34 in 1962). The higher speed of the helicopter allowed rapid deployment across a wide area, bypassing fixed defenses to land troops directly on the objective and avoiding the need to build up a vulnerable beach head before pressing inland. This final point was seen as especially critical during an era in which it was assumed that such troop concentrations would come under attack with nuclear weapons. However, while the LCVP could carry 36 men or 3.5 long tons of cargo, the HUS could only lift 12 men or 1.5 tons of cargo - effectively forcing a reduction in the amount of heavy equipment.

However, another new type of amphibious ship was introduced to rectify this problem - the Amphibious Transport Dock (LPD). The first of these ships, the Raleigh-class of 1962, was built on the 155 meter hull of the Thomaston-class Landing Ship Dock (LSD) and was also equipped with a wet well-deck. But while the LSD was intended to operate as a pure floating dock, transporting and servicing smaller landing craft, the LPD was designed as a multipurpose transport that used its well-deck to operate landing craft more efficiently than the traditional cranes and davits. To this end, the well-deck of the Raleigh-class was just half the length of that on the Thomaston-class, and the saved space was used to increase the number of troops to 1,140 and the cargo capacity to 14,000 square feet and 40,000 cubic feet.

USS Raleigh (LPD-1)

But the Raleigh-class was something of an prototype design and only three ships were built before the first of the substantially larger Austin-class was commissioned in 1965. The new LPD was 173 meters in length with troop capacity cut back to 885 men while cargo space was expanded to 51,000 cubic feet (vehicle space remained constant). However, while the LPD was more flexible and efficient than the older converted cargo ships, the well-deck and aviation spaces imposed a substantial cost in overall capacity - a WWII-era Haskall-class APA had been able to accomodate twice the men and three times the cargo despite being only 80% the size of an Austin-class LPD.

USS Austin (LPD-4)

By 1966, the fleet had grown by 25% and reached its Vietnam-era peak of 188 ships, including 8 LPH, 6 LPD, 28 LSD, 24 APA, 18 AKA, and 104 LST. However, the portion of the fleet that was post-WWII construction was just 24% - slightly less than it had been in 1960. This was because construction on the new large ships proceeded slowly and much of the growth was the result of yet again recommissioning ships built for WWII. But while those ships had still been relatively new during Korea, by Vietnam they were beginning to exceed the two decade mark and the problem of block obsolescence reared its head. The response was three new classes: the 1968 Charleston-class AKA, the 1969 Anchorage-class LSD, and the 1969 Newport-class LST.

The Charleston-class were the first purpose-built AKA (rather than being a modified merchant design) and supplied much of the cargo capacity that was being lost with the retirement of the older ships. At 176 meters, they carried 226 troops, 47,000 square feet, and 88,100 cubic feet of cargo - roughly twice what an Austin-class LPD could accomodate. Like all AKA, the Charleston-class unloaded their cargo via landing craft stored on the main deck, with the standard complement being four 22 meter LCM(8) and five 17 meter LCM(6). Unlike previous AKA, the Charleston-class was equipped with heavier 80 ton cranes. All five members of the class were commissioned by 1970, but in 1969 all AKA were redesignated as LKA to match all the other amphibious ship designations that began with "L" (APA was changed to LPA at the same time).

USS St Louis, LKA-116, the fourth member of the Charleston-class. Note the two twin 3" mounts on the forecastle - the standard armament of amphibious ships of this period.

The Anchorage-class represented a modernization of the LSD fleet, as the last member of the preceding Thomaston-class had been completed over a decade prior. At 169 meters in length it was also a noticeable step up in size, matching the Austin-class LPD. However, the new ships' capacity of 336 troops and 19,700 square feet of vehicle space was effectively the same as that of the Thomaston-class. Instead, the extra tonnage appears to have mostly gone into lengthening the well-deck 39 feet. Five ships of the Anchorage-class were commissioned between 1969 and 1972.

USS Anchorage (LSD-36)

The final new ship was the Newport-class LST. This was a radical departure from all previous LST designs as it replaced the traditional bow doors with a bow ramp - a change that allowed it to match the 20 knot top speed of the rest of the modern amphibious fleet instead of being limited to the 14-17 knots of the earlier post-war LST designs. Interestingly, since the new configuration could not be used to launch LVT amphibious armored vehicles from offshore, the Newport-class also included a small stern gate for that task. But despite the 159 meter length of the new design, its carrying capacity of 386 troops, 16,500 square feet, and 4,500 cubic feet was in fact noticeably less than that of the proceeding 136 meter De Soto County-class. A total of 20 Newport-class ships were built, with the last entering service in 1972.

USS Barnstable County (LST-1197), unloading via the unique bow ramp of the Newport-class

However, despite these new classes, the amphibious fleet continued to decline in size, finally stabilizing at just 69 ships in 1975. However, these ships, which included 7 LPH, 14 LPD, 13 LSD, 2 LPA, 6 LKA, and 27 LST, were now almost entirely large modern designs (the only exception was 7 LST hanging on in minor roles) that were fast, survivable, and equipped with cutting edge equipment such as the CH-46 Sea Knight helicopter (introduced in 1964) and the AAV-7 amphibious armored vehicle (introduced 1972). The much greater size of these new ships meant that even though the 1975 fleet was just 46% the size of the 151 ship 1960 fleet, it still had roughly 60% the capacity in terms of men and materiel.

This force could be considered as representative of the second generation amphibious fleet architecture. The key characteristics of which were the move to larger purpose-built designs and the the replacement of small landing craft with helicopters. This second generation architecture would continue as the model for the remainder of the Cold War, but the beginnings of the shift to the current third generation third generation architecture would be seen the very next year when the first Amphibious Assault Ship, USS Tarawa (LHA-1) commissioned in 1976. This marked the beginning of the trend to even larger multipurpose designs, and will need a post of its own to cover (which I will link here if I write it).