Evolution Of The Amphibious Tank

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By Richard M. Ogorkiewicz - Originally Published August 1957

Although amphibious armored vehicles have come to be recognized as an essential element of an amphibious force, the story of the amphibious tank is one of the least known aspects of the history of amphibious warfare. The reason is largely because it is such a fragmentary story and the practical application of the amphibious tank is still relatively recent-much more recent, for instance, than that of the combat aircraft or of ground combat vehicles.

The conception of the amphibious tank is, however, at least as old as the tank itself. The automotive combat vehicle had hardly begun to take shape when thoughts turned toward applying it to the solution of the age-old problems of crossing water obstacles and of landing from the sea on hostile shores. The connection between the first armored vehicles and the amphibious field was all the more immediate as the first tanks, built in England, were actually sponsored by the British Admiralty and were originally designated as "landships."

The first successful military amphibious vehicle actually appears to have been tried in 1910 by the French Corps of Engineers. This -the Ravailler amphibian- was, however, only a 4-wheeled car. Thereafter practically all the initial development took place in England. In recent years, though, Soviet propaganda has claimed that the first tracked amphibian, as well as the first tank, was built in Russia by Porokhovshchikov, in 1915, a few months before the first British tank.

The first British tanks were certainly not amphibious, being intended principally to break the deadlock of trench warfare into which the Western Front had settled in 1915. But soon alter they appeared, a scheme was advanced for using them in an amphibious raid on the Belgian coast then in German hands. This project was too ambitious considering the primitive state of the original equipment and the whole idea of the raid was eventually abandoned.

Nevertheless, the requirement for a tank which could take part in amphibious operations remained, and shortly before the end of World War I the first tank successfully crossed a water obstacle. This was a British Mark V, a typical 30-ton heavy tank of the period which, after waterproofing and the attachment of a caisson to either side, crossed the river Thames near London in October 1918.

The caisson-flotation method was next considered for the Mark IX, a large infantry and supply carrier, based on the contemporary heavy tanks and, incidentally, the first tracked armored personnel carrier designed and built as such. A much greater step toward an amphibious tank was made after the war with the appearance of the Medium D tank.

The Medium D was one of those rare designs really ahead of its time. It was originally conceived for the mobile component of a massive Allied tank offensive planned for 1919, a force which would strike deep into hostile rear areas paralyzing enemy headquarters and communications while masses of heavy tanks and infantry assaulted his front line. "Plan 1919," as it was called, was never put into practice as the hostilities in Europe ended before it could be executed. But the development work on the Medium D continued, though at a reduced pace - it was almost 2 years after the Armistice that the first tank was built and tested. When it was, however, it exceeded its maximum target speed of 20 mph, which in itself was twice as high as the maximum speed of any other tank at the time. And this in spite of the fact that the Medium D was a fairly large vehicle, almost as long as the LVTP5, and weighed some 15 tons.

The land trials of the Medium D were followed by water trials, which began well, but received a severe set back when the vehicle developed a leak and sank in the Thames near the Woolwich Arsenal, London. The vehicle was salvaged and the development continued with a modified design and a similar but lighter, 8-ton model known as the Light Infantry Tank was designed. Two of the hitter were built by 1922 and on trials proved themselves capable of a speed of up to 30 mph on land and about 11/2 mph in water.

The origin of the Medium D and of the "Plan 1919" was very largely due to Gen (then colonel) J. F. C. Fuller who was Chief of Staff of the British Tank Corps during WW I. After the war Gen Fuller set himself to propagate the idea of armored forces and his prophetic vision illuminated the path of mechanization not only in ground but also in amphibious operations. As far as the latter were concerned, soon after World War I he pictured future landing operations executed by tanks launched from special tank carrying ships. In 1920, in a lecture given at the Royal United Service Institution in London, he even mentioned the possibility of launching tanks from submarine tank carriers-an idea presaging the submarine troop carrier which was experimented with for some time after WW II by the US Marine Corps.

All these revolutionary ideas found little support at the time and the handful of British tank pioneers had to fight hard to retain even 4 tank battalions in the post-war British Army. The development of the equipment ran up against similar difficulties and the Medium D and its derivatives proved too far ahead of their time. Mechanical troubles which were only to be expected with such an advance model were seized upon to condemn it and in 1923, in a wave of financial stringency, it was finally abandoned. At the same time the Government Tank Design Department, headed by Lt Col Philip Johnson, which was responsible for this work was wound up and with it died for a time the first hope of an amphibious combat vehicle.

However, the idea did not die out altogether. Even before the British Medium D and the Light Infantry tanks were abandoned, work had begun in the United States, where the Medium D considerably influenced the design of the first post-war US tank - the Medium A.

Neither the Medium A nor its subsequent developments were amphibious. In 1920, as part of the development of a light reconnaissance tractor for the US Ordnance, the second modification of the Peoria-built model was made amphibious. Five other versions were built between 1920 and 1922, but the development got no further.

Once more, however, the development of the amphibious combat vehicle was taken up elsewhere-this time by J. Walter Christie, who shortly after WW I designed a number of self-propelled gun carriages for the US Ordnance and who in 1922 came out with his first amphibian.

The Christie amphibian has usually been referred to as a tank but more correctly it was an open top, amphibious, self-propelled, 75 mm gun. One of its salient points was the convertible feature associated with Christie designs, which enabled it to travel on tracks or on wheels when the tracks were removed. Another point was that unlike the earlier British Medium D and the much more recent LVTs it was propelled in water by means of two screws instead of tracks. It was rebuilt twice, the second version being longer than the first and the third having 4 bogie wheels per side instead of 3 and being covered in.

The US Army and the Marine Corps tested it and during the trials it swam across the Hudson and the Potomac. In 1923, at Culebra, it gave the first practical demonstration of a mechanized ship-to-shore movement when it swam ashore from the USS Wisconsin. Six vehicles of the second type were procured and were used by the Marine Corps in China, but beyond this there was temporarily no progress and Walter Christie turned his attention once more to ground combat vehicles.

The loss of Walter Christie to the amphibious field was certainly a gain to land warfare for his next and final series of vehicles built between 1928 and 1932 marked a great step forward in armored vehicle design, particularly with regard to high speed suspensions and mobility. Several outstanding vehicles, such as the T3 Medium Tank, were built for the US Army but ultimately Christie was no more fortunate in getting his tanks adopted in the United States than his amphibians.

Two other countries did, however, adopt Christie's tank designs. One was Soviet Russia which purchased 2 Christie tanks in 1931 and copied and developed them on a large scale under the designation of BT, or "fast tanks." It was from the BT series that the T34 medium tank of WW II and the T34/85 of Korean fame evolved, as well as the latest 100 mm gun T54. The other country was Great Britain where a whole series of cruiser tanks-from the A13 of 1938 to the Comet of 1945 -used the Christie type suspension.

In the meantime, in the amphibious field, little happened until the appearance, in 1930, of a new British amphibious tank built by the great shipbuilding and armament firm of Vickers-Armstrong. The tank division of Vickers-Armstrong was the sole designer and producer of armored vehicles in Britain for the greater part of the period between WW I and II and the 2 experimental amphibious tanks which it produced were part of the A4 series of Vickers-Carden-Loyd light tanks for the British Army.

Designated the A4E11 and the A4E12, the 2 Vickers amphibians were light, 7,500 lb. vehicles with a crew of 2 and an armament of a single .303 Vickers machine gun. On land their maximum speed was 20 mph and in water they could propel themselves at up to 3.7 mph by means of a single screw.

The combat potential of such light vehicles was limited though, in all fairness, it must be mentioned that the general trend at the time was toward relatively large numbers of small tanks rather than smaller numbers of more powerfully armed models. Their amphibious capabilities, too, were limited and they were capable of operating only in calm water. Mechanically, however, they were successful and reliable. They attracted a great deal of attention at the time even though the British Army failed to adopt them. Soviet Russia bought 8 samples when this vehicle became available commercially and subsequently went into quantity production with a very similar model designated the T37. A few more of the Vickers amphibians were purchased by China and the Netherlands East Indies.

As far as the Russians were concerned they regarded their light amphibious tanks principally as reconnaissance vehicles, a role in which their light armor and armament were less of a handicap and where their amphibious characteristics were particularly useful. Apart from the T37 the Russians also built a small quantity of large 6-wheeled amphibious armored cars and later a somewhat improved version of the T37, the T38 amphibious tank. The latter, apart from being one of the few amphibious vehicles of its day, also had the distinction of being the first tank carried by air, during peace time Soviet maneuvers in the mid-'30s slung under the bellies of ANT-6 transport-bombers.

Soviet interest in amphibious tanks continued into the early stages of WW II, when almost simultaneously with the introduction of the much better known T34 medium and KV heavy tanks they brought out the T40 amphibious light tank. The T40 did not, however, show up particularly well in the early Soviet-German campaigns thus justifying partly the attitude of other armies which generally showed little interest in this type of vehicle. What little effort was devoted to amphibious light tanks was half-hearted and did not proceed beyond the experimental stage.

In 1935, for instance, the French built a light amphibious reconnaissance tank for their cavalry. This vehicle, the DP2 was, however, damaged and sank during its first amphibious trials. In England, in 1939, Vickers-Armstrong built one more experimental amphibian based on the contemporary British Mark VI light tank. The Czechs built one also, the F4HE, which it was generally assumed at the time, the Germans would take over with the rest of Czech armor after the occupation of Czechoslovakia in 1939. As a result the F4HE appeared in all the 1940-41 British and US manuals of German equipment! In fact, however, the Germans showed as little interest in this type of vehicle as most others and did not continue its development.

The only people apart from the Russians to show consistent interest in amphibious tanks before WW II were the Japanese. Even when the Russians temporarily ceased the development of the T40, when this tank failed to stand up to the combat conditions of the Eastern Front, the Japanese persevered and continued their development right up to the end of WW II.

The Japanese had already shown considerable interest in Christie's original amphibian and in the Vickers-Armstrong model of 1930, and in the early '30s began to develop and build amphibious armored vehicles of their own. Two lines of development were actually pursued, one by the Japanese Army and the other by the Imperial Navy. The latter was generally more successful and produced the best known Japanese amphibian, the Type 2 "Kamisha" light tank of WW II.

"Kamisha" was a 24,500 lb. vehicle with a crew of 3 and an armament of one 37 mm gun and 2 machine guns. As a design it belonged to much the same category as the 1930 Vickers-Annstrong amphibious light tanks and like them was propelled in water by means of screws, but in this case two instead of one. It incorporated, however, one novel feature in the shape of 2 very neat detachable floats-one at the front and one at the rear. These gave the necessary buoyancy and stability in water and being detachable did not impare permanently the vehicle's performance on land.

The detachable float feature was tried on several other vehicles, including the Navy's "Kachisha" 58,-000 lb. heavy amphibious tank. The Navy also had under development a large amphibious carrier, the "Katsusha," while the Army experimented with several light tanks including the "A-Igo" water jet propelled.

All the effort and ingenuity did not, however, bring the Japanese much profit. None of the Japanese amphibians was produced in any quantity. As combat vehicles they were all inadequately armed, and the faulty tactical employment in insignificant driblets condemned them to failure, just as it did Japanese armored forces on land.

In the meantime, well before the Japanese entered the struggle for the Pacific, the problem of amphibious operations arose on the other side of the globe. In 1940, after their victory in France, the German forces found themselves faced with "Operation Sealion" - the projected invasion of the British Isles. One aspect of this problem was that of landing tanks, which were chiefly responsible for the Germany victory in France, and the Germans struck upon the idea of a submerged approach as a means of getting tanks ashore during an amphibious landing.

In essence the submerged landing method amounted to sealing tanks and providing them with snorkel type breathing tubes so that they could be launched off shore in relatively shallow water and move along the bottom until they emerged on the hostile shore. "Operation Sea-lion" never materialized and so this method was never put to test in amphibious operations. It was used, however, with success by German medium tanks during the crossing of the river Bug in Poland on the first day of the German campaign against Russia in June 1941.

Deep fording equipment of the snorkel-tube-type was subsequently incorporated in the design of the famous Tiger I heavy tank, but it does not appear to have been ever used and it did not reappear on later German tanks such as the Panther and Tiger II. The only tracked amphibious equipment used by the Germans was what might best be described as a "tracked tug"-a piece of engineering equipment used chiefly for bridging operations.

When the tide of war changed it was the turn of the British to face the problem of landing tanks-on the shore of the Continent of Europe. They had already pioneered the tank landing craft and this was used for landing Churchill heavy infantry tanks - prepared for fording up to their turret tops-in the amphibious incursion on Dieppe in October 1942. For the main invasion in Normandy, however, the British had developed an entirely novel contrivance for landing tanks, the DD or "Duplex Drive" device.

The DD tank device was the invention of Nicholas Straussler, a Hungarian-born British engineer, who had worked for many years on armored vehicles. Apart from the latter, his designs also included bridging equipment and the DD device was in essence a logical derivative of his collapsible canvas-hulled assault boat. Thus, the DD tank was a standard tank suitably waterproofed fitted with a collapsible canvas hull. When fully extended this hull enabled the tank to float, though unfortunately the tank was well below the water line unable to use its armament until it reached firm ground and the hull could be collapsed.

The DD device was also rather vulnerable to rough seas and enemy fire and the British Admiralty strongly opposed its development. The British Army, however, eventually decided to accept it. It was first tried in 1942 on a Tetrarch light and in the same year orders were given for converting some 650 Valentine infantry tanks into amphibious DD tanks. Curiously enough, like the Soviet T38 amphibious tank, the Tetrarch again linked amphibious with airborne operations. While the T38 was the first tank to be carried by air the Tetrarch was the first tank to go into combat by air-a few having been carried in the large Hamilcar gliders and landed with the British 6th Abn Div on D-day in Normandy.

By 1944, when the Allied armies actually landed in Europe, the Valentine DD tanks had become obsolete and it was decided to convert US-built M4 medium tanks, with which British as well as US armored forces were equipped, into DD amphibious tanks. Several hundred were converted in Britain just 5 months before D-day, on the personal intervention of Gen Eisenhower.

By D-day several British and 3 US tank battalions were trained and equipped with DD M4 medium tanks. In the British landing zones they were used with some success though on account of rough weather many could not be launched in the water and had to be landed in the normal way from landing craft like the rest of the British assault armor. It was the latter rather than the DD tanks which was vindicated. Altogether, the armor landed with the assault waves in the British sector amounted to 3 armored brigades and many special units of mine sweeping and assault engineer tanks. Their performance earned them high praise from Allied commanders.

Compared with the British, the use of tanks in the American sector was limited. Of the 2 US DD tank battalions which were deployed, only one was launched as intended and of this only 2 tanks reached the shore, thus justifying some of the British Admiralty's worst fears about the DD device.

Throughout the early stages of WW II the US Army confined its efforts in the sphere of amphibious tracked vehicles to the light tractor which was standardized as the M29 and which was actually originally intended for oversnow operation. It was only in the latter part of the war that the Ordnance Corps built the T86 and T87 amphibious selfpropelled guns based on the 76 mm M18 tank destroyer and proceeded with the development of tank flotation methods based on large detachable steel floats.

This last method was similar in principle to that used on the "Kamisha" and other Japanese amphibious tanks and had the great advantage over the British DD approach in that it was far less vulnerable and it also enabled the main armament to be used while in water. Its great disadvantage compared with the DD device was the size of the floats and the consequent demand on shipboard space. For instance, the M19 swimming device developed for the M4 medium tank increased its length from 19 to 47 feet and its width from 81/2 to 11 feet.

The work on the swimming devices was actually begun in 1943, but by the end of WW II it had not progressed far enough for them to be used in action. The same applied to the T86 and T87 amphibious selfpropelled guns. Work on the swimming devices was subsequently transferred to the M26 and then the M46 medium tanks but, in the meantime, the Army followed the example of the Marine Corps and adopted the LVT as the most practical solution available at the time.

The Army's adoption of the LVT and the formation of Army amphibious tractor battalions was all the more noteworthy for the fact that originally, in 1942, the Armored Board rejected the LVT as too vulnerable. The British adopted the LVT also and made some use of it, as well as of DD M4 tanks, in the crossing of the Rhine in 1945 in the final phase of the war in Europe. When the war ended a special LVT assault brigade of the Royal Marines was being formed for service in the Far East and deliveries begun of the British-built version of the LVT designed and manufactured by the British Nuffield organization and called the Neptune.

The story of the LVT, from Don-ald Roebling's rescue amphibian of 1936 to the recent LVTP5 has been fully and authoritatively told by LtCol Croizat in the June 1953 GAZETTE. Suffice it here to mention only one point: unlike all the other amphibious combat vehicles, the LVT was not an armored vehicle which was made amphibious, but it was basically an amphibious vehicle adapted to combat needs. Originally, of course, it was only intended as a logistic vehicle and while the first production vehicles were delivered by the Food Machinery Corporation in 1941 it was not until 1942 that the armored version was produced; heavy turretted armament came later still.

The fact that the LVT is primarily an amphibian vehicle carries both advantages and disadvantages. The advantage is that its water performance is far superior to that of any ground vehicle adapted to amphibious needs. Its disadvantages are out of water. They are similar to those of the original British Medium D, i.e. large silhouette and overall dimensions and relatively thin armor, so that it can not compete too successfully with ground combat vehicles on land.

However, these facts do not mean that the gap between the characteristics of the amphibious and ground combat vehicles cannot be considerably narrowed. The M59 armored personnel carrier, built for the US Army by the Food Machinery Corporation on the basis of their wide experience with the LVT, is a clear indication of what might be done. Admittedly, the M59 has only limited amphibious characteristics, but that does not apply to its Marine counterpart-the LVTPX-2.

The solution to a versatile amphibious combat vehicle will be all the more feasible if the present trends in armorpiercing weapons continue and the relative advantages of armor protection diminish further. The probability that armor will be more easily penetrated will not mean that armor protection will become useless or, even less, that armored vehicles themselves will become obsolete, for armor protection has never been the tank's principal characteristic. It will mean that a limited degree of protection will have to be definitely accepted and more emphasis placed on fire power and mobility. This, however, would only be logical for the tank is fundamentally a weapon carrier, a mobile ground platform, or, as a recent British definition put it, a "vehicle to carry fire power."

Positive signs of a trend toward this conception and toward lighter armored vehicles have recently been provided by the Marine Corps "Ontos," the US Army's 90 mm "Spat" and the French Army's AMX 13 airtransportable tank. Further extension of this trend toward light-er-weight vehicles would certainly hold more promise than trying to bestow amphibious characteristics on the present day 40 or 50 ton medium tanks, whether by the DD approach pursued by the British Army or the detachable float methods developed by the US Ordnance.

However, applied to lighter vehicles the detachable float method might well produce a very acceptable amphibious vehicle which would, after jettisoning its floats, be capable of equally efficient ground operation. Trying to design permanently sufficient buoyancy into an armored vehicle will continue to incur the penalty of large silhouette if full amphibious capabilities are required, but if limited characteristics are acceptable a satisfactory solution can be reached by this approach. This is shown by the recent Soviet light amphibious reconnaissance tank, which also demonstrates continued Soviet interest in amphibious tanks.

On the armament side, a successful light amphibious tank is certainly more likely to be achieved. Powerful, light weight armament which was not available in the days of the original Vickers-Armstrong amphibians and the Soviet T37 and T38, and whose absence was largely responsible for their failure, exists now in the shape of various recoilless weapons and short range guided missiles, such as the French Army's SS 10 anti-tank missile. Thus the solution which has eluded earlier designers because of the lack of suitable armament might now become a reality and the various attempts be finally consolidated into a successful amphibious tank.

In the meantime the need for an amphibious tank remains as great as ever. It alone can provide an amphibious force with the medium-range, mobile fire power which would complement on one hand the short-range fire power of the infantry and on the other the heavier fire power of the artillery, aircraft and naval guns or missiles. The development of an amphibious tank is, therefore, well worth all the effort which can be devoted to it. Its final version should be capable not only of efficient movement on land and in water but also of being lifted by air when required, in keeping with the latest trends in amphibious doctrine toward vertical envelopment.

(As of Aug. 1957) Mr. Ogorkiewicz is a development engineer for Humber Ltd. of the Rootes Motors Group. Born in Poland, he received his advanced education at the Univ. of London where he lectured in mechanical engineering until 1952. Before joining Rootes, Mr. Ogorkiewicz was with the Eng Div of the Ford Motor Co, Ltd. in England. He has published articles in military periodicals throughout the world including 46 pieces in ARMOR. He collaborated with B. H. Liddell Hart in writing the chapter on tanks in the book "The Red Army."