M65 Assault Gun

The M65 Assault Gun, also called the M65 Tank Destroyer - Officially, "105mm Gun Motor Carriage, Tracked, M65" - is an American military vehicle based upon the modified chassis of older M48 Pershing tanks (which are being phased out in favor of the newer M60 model). The M65 was intended to prolong the useful service life of the American Army's huge numbers of M48 tanks, and was developed out of the U.S.'s experiences during the Great War and the Winter War (Alaska campaign). Infantry needed their own, organic close fire support in order to adequately assault fortifications, and this support needed to be able to weather artillery and smallarms fire at the very least in order to advance. What started as a sort of self-propelled artillery concept quickly became an easily-produced and very common multirole vehicle. The design was more easily produced and maintained than the tanks upon which it was based, while the heavy rigid casement allowed it to have heavier armor than a turret - especially on top, to protect against plunging shell-fire. It was was fitted with a variant of the new 105mm rifled gun that armed the M60 Pershing tank, rather than the older 90mm gun of the original M47/48 Pershing tanks, and one of the most beloved and ubiquitous vehicles in the American arsenal was born.

Design
The M65 Assault Gun is built upon a modified M48 Pershing tank chassis, using the newer V12 twin-turbo air-cooled diesel of the M60 (which, conveniently, is just a newer iteration of the same engine) as well as its commander's cupola, aluminum road wheels and transmission. This altered M48 body, in place of a turret, is fitted with a low-profile, sloped-armored casement mounting an M68A3 105mm Rifled Gun firing through a limited-traverse mantlet at the front-center of the structure. This weapon is a derivative / variant of the standard M68A1 L/55 gun on the new M60 Pershings (and represents a significant improvement over the 90mm main armament of the older M48 tanks upon which the M65 Assault Gun are based). This particular -A3 model of the M68 105mm cannon - designed specifically for use in the M65 - has a modified stabilization system and breech block, as well as a longer barrel (64 calibres rather than the 55 calibres of the M60 Pershing's -A1 version).

Secondary Armament consists of three Browning .50-calibre heavy machine guns: one on the front of the casement to the right of the main gun in an articulating semi-hemispherical ball mount, another fitted to a pintle on the loader's hatch (right side of the casement roof) and a third in a rotating commander's cupola, a "mini-turret", atop the chassis on the left side of the casement roof, more toward the front. This cupola, as mentioned above, is also taken directly from the M60 tank.

The M65 Assault Gun is internally sealed with air filters to protect against chemical and biological attacks. It also carries a snorkel kit that allows it to be quickly converted to drive through riverbeds in absence of a bridge. It has a crew of five - Driver, Gunner, Commander, Loader & Radio Operator (who also mans the forward machine gun) - with five Thompson Submachine-guns in the cabin should the crew be forced to evacuate the vehicle.

Standard post-production fittings for all M65s include a night-vision infra-red light and scope system, cold weather modifications to the engine and air filters, detatchable external fuel tanks, spare track links, spare road wheels and spaced armor skirts (see StuG IV picture above) to protect against shaped charge weapons like RPGs and Bazookas. M65s are also being fitted in the field with a newly-developed cage armor system to extend this extra level of protection to the front and back, as well, but this has so far only reached a minority of operational units.

Operational Employment
The M65 assault gun is a multipurpose infantry support vehicle that operates as an integral element to Infantry Regiments, partially replacing their detatchments of towed anti-tank guns (a company of heavier 125mm towed AT guns is still retained). It also serves as a replacement for proper tanks in National Guard units, because it is cheaper and more easily produced / maintained. By now, all active Army, Marine and National Guard units have received their compliments of M65s, making the vehicle extremely ubiquitous. Derivative models - such as the M65A2 Infantry Gun with a heavily modified M114 155mm howitzer - serve other important roles within Infantry and Armored Regiments.

M65s are especially fearsome when used for assaulting fixed enemy positions and in urban combat, where their more-evenly distributed armor is an asset and their heavy-calibre guns can knock holes buildings to clear them of enemy troops or make a path for American soldiers. The Howitzer and Flamethrower variants of the vehicle are particularly prized for fighting in the narrow, Old World-style towns of Russian Alaska. The baseline M65 with its powerful 105mm rifled gun also makes an extremely effective tank destroyer, using its lower profile (and often a numerical advantage) to ambush, overwhelm and shatter formations of Imperial tanks. The Assault Guns can also go head-to-head with Russian T-55s in open country and, unlike their M60 counterparts, are often able to match or exceed the massed Imperial tank formations in size. The longer, slightly heavier gun (105mm L/64 vs the Russians' 100mm L/53.4) is also more powerful. M65 are, however, completely outmatched in a head-to-head clash by the enemy's Iosef Stalin heavy tanks (which have  very thick, heavily-sloped armor and powerful 122mm guns) - yet they are still more than capable of crippling these behemoths in an ambush situation. More than one Russian heavy tank has been knocked out by a phantom shot from an M65 hiding amidst rubble, snow or trees without ever having had the time to respond.

Advantages

 * As mentioned above, the M65 has a much lower profile than the M60 or M48 Pershings. It is also shorter than the T-54/55, but the difference is much less pronounced (the M60 being unusually tall and the T-54/55s being designed for maximum compactness).


 * The method by which the M65's gun is mounted, through its hull in a much more stable position, perceivably improves the cannon's accuracy when compared to a conventional tank turret arrangement while also permitting a longer barrel without it becoming unwieldly


 * The placement of the M65's machine guns - particularly the bow-mounted, independently-articulating position rather than a coaxial mount - are better positioned to offer suppressive / anti-personnel fire in defense of the vehicle. The M65 also has one more machine gun than the T-54/55, which lacks any kind of MG on the loader's hatch (having only a coaxial 7.62mm and a heavy 14.5mm atop the turret).


 * The M65's armor scheme is superior to that of a conventional tank in terms of all-around protection. While the maximum thickness is not really greater, the reduced surface area (compared with the M60 especially) afforded by its low-profile and casemented, turretless structure permits the plating to be better spread around the chassis. This makes the M65 more suited for urban combat and better able to survive the close-range shaped charge attacks of enemy infantry (i.e. RPGs).


 * The M65 is considerably less complex overall than a tank - due to its simple casemented construction which dispenses with the turret, among other more minor things - and is therefore considerably more economical to manufacture, both in terms of cost and production time. The decision to base the new vehicle on the proven M48 chassis (which American industry had by then become very adapt at producing and which was already widely available in surplus / reserve stocks that could be readily converted) further reduced the M65's per-unit expense. But, even more importantly, this design choice enabled a large fleet of the new assault guns to be built up and deployed for action very quickly. By 1962, however, supplies of left-over / un-used M48s have all but dried up, with new M65s (not to mention the myriad of other AFVs derived from said tanks) being produced in factories instead.


 * The M65's configuration and shape / silhouette allow it to take full advantage of a "hull-down" position (i.e. being dug in behind a crest or piece of raised ground in such a way that most of the hull is obscured and only the turret or upper structure is visible - the tank / AFV equivalent of infantry firing while crouched or prone behind cover). The M60 tank, comparatively, thanks to its substantial height, can "dig in" at a very steep angle and is generally regarded as one of the world's best tanks for the use of the "hull-down" tactic. Even so, a substantial part of its rather tall turret will inevitably remain exposed. Meanwhile, the T-54/55's extremely compact size (a mere 2.4 meters in height) and squatty shape make obtaining a satisfactory, effective "hull-down" position exceedingly difficult. The small amount of clearance between the Russian tank's chassis and gun barrel means the main cannon can barely be depressed below horizontal at all. Thus, firing along a horizontal trajectory from all but the most shallow-angled slopes is impossible. However, concealing the small T-54/55 completely (i.e. a "turret-down" position, where nothing is left exposed) is very easy. The unique configuration of the M65 imparts it with the advantages of both of vehicles: it is compact like the Russian tank, but becomes almost invisible (considerably more so even than the M60) in a proper "hull-down" position.


 * The M65's configuration also gives it more interior room than the M60 (and supremely more so compared to the U.S. tank's squat, cramped Russian counterpart). This means a better working environment for the crew: they have more room to maneuver and are not separated into two different sections of the hull, since the M65 lacks a turret. Space inside the assault gun is sufficient that, in emergencies, the crew can use their vehicle to protect wounded soldiers by driving over them and then pulling them up inside through the emergency belly hatch.


 * Finally, the M65's chassis is an ideal platform upon which to create specialist vehicles, since using a tank as the base would - in most cases - necessitate the removal of its turret anyway.

Disadvantages

 * While the main gun of a tank sits in a turret capable of complete circular rotation, the M65's cannon is mounted longitudinally through its hull with heavy bracing for maximum accuracy when firing from a stationary position or when moving forward at speed. Thus, it has only very limited traverse (horizontal movement) capabilities. For lateral adjustments of more than a few degrees, the M65 must therefore pivot its entire chassis - a process which is considerably slower than simply revolving a tank turret and, even worse, also exposes the vehicle's thinner side armor. This limitation is problematic if/when the assault gun must address sudden threats to its flanks or rear (i.e. ambushes) while it is on the move, as it must slow down or come to a halt and then turn about on its axis to bring the gun on-target. However, apart from that rather specific scenario, the disadvantage of limited gun traverse is largely situational: there are few actual recorded instances of U.S. assault guns being at any real disadvantage while on the offensive because of their inability to traverse their guns 360°.


 * Continuing in this vein, however: should a casemented assault gun such as the M65 become immobilized, it will no longer be able to bring its gun around to deal with threats. A tracked fighting vehicle can be "ham-strung" in such a manner by all sorts of things: from mines to small-calibre shellfire, traps to hand-thrown grenades... and even by particularly unfavorable terrain. This has traditionally been one of the greatest weaknesses / sources of vulnerability for the tank, as infantry at close range have a myriad of ways to stop them cold. The M65 - which was designed as an organic armored direct-fire platform to support attacking infantry (and only later began to see use as a defense- / ambush-oriented tank destroyer) - is supposed to be more useful, or at least less vulnerable, in urban combat: where a tracked AFV is at the greatest risk of immobilization. On the whole, this theory holds up in practice (primarily due to the nature of the vehicle's armor layout) - but the M65 remains extremely vulnerable to being immobilized and then flanked, even so. A ham-strung American assault gun stuck in a narrow street serves as little more than a roadblock, since its operators will have abandoned it in short order.


 * Ultimately, the advantages of the M65 over traditional tanks (economy and ease of production not-withstanding) are all situational, despite the fact that it has seen a much broader range of applications beyond its original, limited, intended infantry-support role. In defensive combat and in large, open, set-piece-type combined arms battles, the assault gun's disadvantages are not especially problematic. However, the M65 and other such platforms simply cannot boast of a tank's tactical flexibility. This is perhaps the reason why the Russians - whose AFVs are designed primarily for, and used primarily in, large formation-based (set-piece) massed attacks - have chosen to produce huge numbers of cost-effective tanks rather than place more emphasis on the assault gun concept (which one might think better-suited to that sort of warfare). Because even when not designed with it in mind, a tank has inherently more tactical flexibility than an assault gun or tank destroyer.
 * The final important disadvantage is purely economic / logistical and more in the long-term. The creation of the M65 was, fundamentally, a cost-effective (if innovative) way to make use of large stockpiles of outdated equipment (the roughly 13,000 M48 Pershings in U.S. service at the start of the Winter War which had suddenly become obscelete almost over-night). Yet the steady progression of technology will, at some point in the future, almost certainly require the production of an entirely new and original design of assault gun - not based on repurposed surplus tanks - if the United States wishes to continue effectively employing that type of AFV. At this point, the necessity of the assault gun's very concept will certainly be called into question, as one of the biggest motivating factors behind its adoption will no longer apply. However, only time can tell.

Models

 * 105mm Gun Motor Carriage, Tracked, M65A1 (M65A1 Assault Gun) - Standard Version described above


 * 155mm Gun Motor Carriage, Tracked, M65A2 (M65A2 Assault Howitzer) - Self-propelled infantry support artillery vehicle armed with a short-barrel derivative of the M117 155mm howitzer for anti-infantry and fortification assault missions. Tandem / parallel design to the standard assault gun model (i.e. both were planned from the outset). Produced on a rough 1:2 ratio with the M65A1 (i.e. one assault howitzer for every two assault guns).
 * Motor Carriage, Tracked, Command & Reconnaissance, M65A3 - Command & Control, Recon and spotting variant of the M65 with an auto-loaded 50mm cannon derived from the American anti-aircraft autocannon of the same calibre.
 * 127mm Gun Motor Carriage, Tracked, M65A5 "Super Wolverine" - field-tested prototype variant of the base-line M65A1 Assault Gun boasting a more powerful 127mm anti-tank gun (a derivative of the 127mm Heavy Gun M144). 32 were produced including the two demonstrator prototypes, with 30 combat-outfitted examples made in a limited-production run and sent to units in the Army of Northern Virginia for evaluation. This variant was never put into proper production and was scrapped in favor of the 127mm Gun Motor Carriage M145 (a simple self-propelled version of the M144 Anti-tank Gun).


 * M65A6 Assault Vehicle (M65 "Zippo") - Self-propelled flamethrower variant with an M6-7 flamethrower


 * M65A8 Engineering Vehicle - Engineering vehicle for mine laying and demolition work. Very similar to the M728 Combat Engineering Vehicle


 * M65A10 Armored Recovery Vehicle - Armored Recovery Vehicle with crane and towing rig

Organization
There are several different tactical / battlefield organizational schemes considered "assault gun units", although none of them actually have "assault gun" in their designation.

Background
Prior to the wide-scale introduction of the M65 assault gun, U.S. infantry divisions had no large independent anti-tank components. Each infantry regiment had a battery of lighter towed anti-tank guns and the Division as a whole would have a heavier AT battalion attached directly to the HQ from the Corps reserve. Even though these battalions were not technically an integral part of the unit, the relationships became essentially permenant and habitual: i.e. the Corps would always attach the same AT Battalion to a given Division, to the point that it might as well have been a permenant part of said Division. However, the conditions of the Winter War caused a major upset ton the thinking and modes of operation in the U.S. Army. A unique version of the Combined Arms principle emphasizing massive, heavy, overwhelming firepower became the new order of the day. The idea was to cut down on casualties and improve effectiveness by augmenting the "fire elements" (i.e. big guns), and reducing the manpower, of each Division, but particularly the Infantry Division. As such, the structure of the U.S. Army Infantry Division was changed from the traditional "triangular" - i.e. three infantry regiments - scheme used by most of the world to one having only two infantry regiments. To compensate for this, said regiments were enlarged somewhat, and the "gap" was filled with more AFVs,  Artillery and other battlefield support elements.

Around this time, two new distinctions entered into common American organizational tables: the Brigade and the Detatchment.

Brigade
Brigades were not a new concept and had been employed in various incarnations since the conception of the U.S. Army, but the use of the term and the perameters defining it now evolved considerably (with many Regiments being retroactively re-designated as Brigades once the new concept was implemented). A Brigade under the current definition is a more specialized equivalent of a Regiment which incorporates a broader scope of unit types and/or somewhat larger (i.e. a Regiment typically has 3-5 Battalions, a Brigade 3-6). In essence, a given unit will be called a Brigade to denote that it is somehow irregular in structure or operation - usually for at least one of the following reasons:


 * The unit is either organizationally independent of any Division (usually directly under an Army Corps, Field Army or Group Army HQ), or else is part of a Division but intended to be capable of independent operation [whereas Regiments are integral components of a Division and dependent upon other Regiments within said Division to function]


 * Its component Battalions are of multiple Arms of Service and/or it has a larger number of Battalions than would be normal


 * It functions organically within a Division but operates in broken up sub-units (this is especially true of artillery)


 * In a few cases, a Brigade in U.S. terminology is a grouping of multiple (usually two) regiments, often also incorporating at least one independent battalion-sized unit of a different Arm of Service. The most notable example of this case is in U.S. Armored Divisions, which have two Brigades each with two Tank Regiments as well as a Battalion's worth of self-propelled artillery. Note that this specific use of the term Brigade - i.e. a grouping of 2-3 regiments - is the term's oldest definition, but also probably the least common one in modern times.

Detatchment
The second distinction / term is entirely new and unique: a Detatchment, which is an alternative equivalent to a Battalion. Using it in place of Battalion basically has the same qualifiers as for Brigades, but Detatchment is also used more generically for support personnel and battalion-sized units attached directly to formational headquarters (Division, Corps, Field Army or Group Army HQs). Thus, for example, the Pioneers [Combat Engineers] and various supply troops incorporated into a Division's command element are Detatchments rather than Battalions.

The Anti-Tank Brigade
Each modern-format U.S. Infantry Division has, in place of the Infantry Regiment it gave up, what's called an "Anti-Tank Brigade". This is, in essence, an assault gun formation with additional elements and supercedes the older Divisions' towed AT guns (which are no longer used). The Anti-Tank Brigade has two "Mechanized Anti-Tank Detatchments", each with a total of 45 M65 Assault Guns, that break down into three "Assault Batteries" [battery being the Artillery Arm's term for companies, used in this case because the assault guns are technically a form of anti-tank artillery, at least in the context of formal organization - in practice, they are more like Armor].

An Assault Battery has 12 M65A1 105mm assault guns in four platoons of three plus a battery HQ element with one M65A3 command variant for the Captain and one M65A8 engineering variant to be used as needed - 42 AFVs in all. The M-AT.Dmt [formal abbreviation of "Mechanized AT Detatchment"] further has an HQ element of its own with three additional M65s: two command (for the CO, who is either a Major or Lt. Colonel, and the XO - either a Captain or Major) plus one engineering model. The total is thus 45 M65s of various types: 36 105mm assault guns, 5 command tracks and 4 engineering tracks.

Rounding out the Brigade's AFV complement is a third assault gun Detatchment, called a "Mechanized Howitzer Detatchment" [M-Fh.Dmt]. M65A2 Assault Howitzers, armed with a short barreled derivative of the M117 Gun-Howitzer. This unit is organized the same as the regular assault gun Detatchments: 36 howitzer tracks, 5 command tracks and 4 engineering tracks. Normally, the howitzer Detatchment is broken up and two Batteries are assigned to provide close indirect fire-support to each assault gun unit, which themselves operate in support of the Infantry Regiments.

The Anti-Tank Brigade also contains a Detatchment of 127mm Anti-Tank guns, usually a mixture of the M144 towed pieces and M145 self-propelled carriages (depending on the unit, as there aren't enough M145s to go around). Usually there are two Batteries of 9 towed guns each and one Battery of 12 self-propelled guns organized in the same manner as the Assault Guns (4 platoons of 3), plus an integral battery of 12 self-propelled 50mm anti-aircraft tracks (and their supporting vehicles with radar, spotting equipment, etc). The Detatchment also as a "Support Battery" of half-tracks to provide the necessary logistics and such (spotting, surveying of firing positions, etc).

The Independent Anti-tank Brigades
These units are called "Mechanized Anti-tank Brigades" to differentiate them from the ones integral to an Infantry Division. They are incorporated into Army and Group Army HQs, to be moved around their respective commands' theatres of operation as required (i.e. wherever additional firepower is needed). Thus, a given Corps in heavy fighting will have one of these Mechanized Anti-tank Brigades [M-At.Bde] attached to them for as small a window as one day before it is moved somewhere else.

The sub-units of these independent assault gun Brigades are organized in the same way as those of the regular Brigades, but they have a different arrangement of them. Each has two Detatchments of M65A1 Assault Guns and two of Assault Howitzers, plus one Battery of M145 self-propelled 127mm AT guns and another Battery of 50mm AA tracks.

Production History
Designed: 1959-1960

Produced: 1960-present

Manufacturer: Detroit Arsenal Tank Plant, Chrysler, Ford Motor Company

Specifications
Weight: 50 Tonnes metric / 55 Short Tons

Length, overall: 9.6 meters / 31.5 feet

Length, hull: 6.4 meters / 21 feet

Width, without armored skirts: 3.65 meters / 12 feet

Width, with armored skirts: 3.8 meters / 12.5 feet

Height: 2.25 meters / 7.38 feet

Track Width: 711.2mm / 28"

Crew: 5 (Commander, Gunner, Driver, Loader, Radio Operator)

Armor: 180mm / 7.1" maximum

Main Armament: M68A3 L/64 105mm Rifled Gun

Secondary Armament:


 * .50-calibre M2 Browning Heavy Machine Gun in ball turret - front glacis, right side
 * .50-calibre M2 Browning Heavy Machine Gun in independent cupola - commander's roof hatch, left side
 * .50-calibre M2 Browning Heavy Machine Gun on pintle mount - loader's roof hatch, right side

Engine:  Continental AVDS-1790-5 V-12, air-cooled, Twin-turbo diesel (800 hp / 671 KW)

Transmission: General Motors Cross-Drive transmission, 2 gears forward, 1 gear reverse

Suspension: Transverse torsion bars

Ground Clearance: 406.4mm / 16"

Fuel Capacity, without external tanks: 760 litres / 200 U.S. gallons

Operational Range, without external tanks: 450 km / 279.6 miles

Road Speed: 48 km/h / 30 mph