INTRODUCTION
“On the battlefield of the future, enemy forces will be located, tracked and targeted almost instantaneously through the use of data links, computer assisted intelligence evaluation and automated fire control. With first round kill probabilities approaching certainty, and with surveillance day ices that can continually track the enemy, the need for large forces to fix the opposition physically will he less important. 1 see battlefields on which we can destroy anything we locate through instant communications and the almost instantaneous application of lethal firepower. No more than ten years should Separate us from the automated battlefield …….This version of the future battlefield was described an long ago as 1949 by General W C Westmoreland, then Chief of Staff, US Army. Developments in weapons technology have not proceeded as fast as the General had predicted, or perhaps honed, but military scientist are close to turning his vision into reality. On current evidence, the battlefields of the early 1990s will be exactly as described by General Westmoreland.
The battlefield of the future can be expected to be dense with sophisticated combat systems whose range, lethality and employment capabilities surpass anything known in contemporary warfare. The airspace over the battlefield will be saturated with aerial and space surveillance, reconnaissance and target acquisition systems. Air defence weapons will exist to deny or degrade the use of these aerial platforms. Rapid technology advances are changing the very shape, scope and speed of warfare, quite literally turning science fiction into science fact. Microelectronics, computer-aided controls and intense materials research are propagating more deadly weapons and countermeasures in the air, at sea, on the ground and, increasingly, in the ‘final frontier’ – space.
This article examines the recent developments and those which are likely to take place in land based weapons technology, in two parts. Part I covers advances in armoured fighting vehicles, field, air defence and nuclear artillery and battlefield surveillance. Part IT, to published in a future issue, will include attack helicopters, ATGWs, night vision devices, communications technology including electronic warfare, automated command and control systems and the effects of developments in weapons technology on future tactics.
Mature Weapons Systems
The fundamental design criteria of main battle tanks (METs) are by now well established and the operation products represent the compromise or ‘trade-off ‘between firepower, mobility and protection, with emphasis Being laid on either one or the other by different armies. because of the conflicting requirements of the basic criteria, it is extremely difficult to optimise all of them in one MBT. However, NATO’s Leopard 2 of FRG, Challenger of UK, AMX 30 of France and Ml Abrams of USA and the soviet -Warsaw Pact T-72 and T-80 series of MBTs, all represent mature weapons *nature systems.
Mobility
Present and future tank designs are considerably more complex and heavier than earlier models. For example, Leopard 2 of FRG and Abrams of USA both weigh about 55 tons. Chieftain’s replacement, Challenger of U.K., will weigh about 60 tons. Increased weight means that more powerful engines must be provided to retain the same degree of mobility. The Soviet Union has for long maintained the weight of their METs at 40 tons or less. But, the T-80, equipped with heavier compound armour, is likely to weigh between 45 and 50 tons. Weight has a direct effect on speed, mobility, size and endurance.
A critical factor in a tank’s height is the loader who must stand upright to be able to feed rounds into the breech. Automatic loading allows the tank’s height to be lowered, thus reducing weight and silhouette. The loader is eliminated while maintaining the same concept for turret design, with the commander and gunner sitting inside the rotating mass of the turret. A more radical solution is to move the two down into the hull, thus enabling the turret to be made very much smaller, as on the Swedish EDES – 19 Topless turret design. In this developmental model, an articulated loading arm reloads the external gun within two second, regardless of barrel alignment. Designer are now thinking in terms of reducing the tank crew to two and speculation about one-man driven and operated tank (like fighter aircraft), are no longer considered quixotic. However, such reduction will generate its own attendant problems of crew fatigue, casualties and maintenance, besides being psychologically ill-advised.
Firepower
The increasing lethality of guns has been exemplified by the T-54/T-55 with its 100 mm gun firing 3 rounds per minute (RPM), the T-62 with a 115 mm smooth bore gun firing APFSDS rounds with a 4 to 6 RPM capability. The NATO nations went from the US M48 with its 90 mm gun firing HEAT rounds and the British Chieftain with a 105 mm gun firing APDs rounds to the new Challenger’s 120 mm gun which, like Leopard 2, fires the modern APFSDS ammunition. Till 1984, the US M1 Abrams and the French AMX 30 tanks mounted 105 mm guns (firing ADFSDS), but since then MIE1 Abrams (and earlier tanks, in a retrofit programme) is mounting the 120 mm German smoothbore gun.
Main gun ammunition has undergone many refinements in both kinetic energy projectiles (APDS, APFSDS) and chemical energy projectiles (HEAT, HESH).and Depleted uranium is replacing tungsten carbide in APFSDS rounds. HEAT shells are becoming more efficient with improvements in liner technology.
Protection
In response to the shared charge, British scientists developed a composite, laminate armour called Chobham armour. This compound armour employs layers of metals, ceramics and Plastics which absorb and break up the high velocity and shaped charge rounds, enabling the tank to survive otherwise disabling or fatal hits. As a countermeasure to the long rod penetrator of APFSDS rounds, a new type of “reactive” or ”active armour, using an explosive charge in its outer surface, has teen recently introduced. Reactive armour consists of bolt-on sections which explode when hit by an anti-tank projectile. This dissipates the jet of a HEAT round, reducing its effect, and may deflect an APFSDS round enough to prevent penetration. The Israeli’s are reported to have used active armour on 48 and Merkava tanks during their Lebanon campaign. The additional sections add approximately one ton to the weight of the tank.
Individual tank designs have often experimented with simple innovations to improve the protection given by armour plates. If a tank’s armour is applied at 60 degrees of slope, it doubles the distance or thickness which a projectile must penetrate. The Soviet T – 72, the American Abrams and Sweden’s S tank, all have a high slope on their hulls. The British Chieftain has a high slope on the turret.
However, frontal arc protection is perhaps the least of the tank designers’ worries today. The top of the tank is its most vulnerable and least protected portion and it is for this target that future ATGWs are being developed, including some artillery delivered anti-armour systems. Major reshaping of the overall structure of tanks is inevitable to ward off the new threat.
The newer tanks all have infra-red or thermal imaging night sights, Laser range finders and ballistic computers for fire control, enabling them to open fire on a target within seconds of sighting it, with a very high kill probability. The night sights now in use allow accurate firing upto about 1500 meters.
Basic data of present and future MBTs are at Table 1 (All Tables are at the end of the article).
Robot Tanks of the Future
Radical proposals are being made for remote controlled, automated robot tanks. The concept is attractive and in line with recent advances in robotic technology. A US Army study in 1983 pointed out, “Because of high manpower costs and declining birthrates, robots will be needed, particularly on certain high-risk missions. Robot ‘pointsmen’ could detect booby traps or ambushes and warn human soldiers following behind. Robotic tanks could roam the battlefield, locating or planting mines. They could operate uninhibited in nuclear, biological or chemical environment.”
The US Army has begun development of an “autonomous land vehicle” – a tank like device capable of manoeuvring around an open battlefield using artificial intelligence. A new prototype machine called PROWLER (Programmable Robot Observer With Logical Enemy Response), is a motile robot sentry resembling a miniature tank. The current model has two M 60 machine guns and a grenade launcher. The final form will be equipped with microcomputers with artificial intelligence software and distance-ranging sensors, allowing it to patrol the perimeters of areas such as airfields, military bases and storage depots, fully capable of identifying intruders. However, a robotic MBT is still a distant dream.
Infantry Combat Vehicles
The first generation armoured personnel carriers, regarded as “tattle taxis”, can be thought of as re-establishing the dragon an infantryman who rides into battle but fights on foot. The soviet EMP was the first infantry combat vehicle (ICV) which combined the ability of troops to fight while mounted, with considerable firepower being provided by the ICV in support its section.
At the time of its introduction into service in 1970, the BMP 1 was clearly the best production model. ICV in service with its 73 mm smoothbore gun and the Sagger ATGW. It retained its supremacy until the German Marder was introduced a few year later. The current model of Marder mounts a 20 mm smoothbore gun in its turret as well as the MILAN ATGW. The Marder is protected than BMP although it is not amphibious. The Marder weighs 29 tons against BMP’s 16 tons.
The newest ICV to enter service with a major army, the US Army, is the Bradley Fighting Vehicle System, Popularly known as the M2 Bradley. It is a sophisticated and well equipped vehicle which is the culmination of many years of development and dispute over design philosophy. The M2 Bradley is equipped with heavy armament and is specifically intended to fight in company with the MI Abrams MBT. Weighing 22.7 tons, this ICV can carry one infantry section which can fire either mounted or dismounted. It has a two-man turret mounting a 25 mm stabilised gun, its primary weapon, supported by the TOW ATGW and a 7.62 mm coaxial MG. Its “space laminate” armour is designed to protect against small calibre weapons, provide overhead protection against artillery airbursts and hull protection against anti-personnel mines. The commander and gunner are both Provided night vision devices. However, the M2 Bradley’s aluminum armour is vulnerable to all HEAT rounds such as the RPG-7’s, as aluminum vaporises quickly when struck by HEAT rounds.
The ICV is not universally accepted as a potent as a potent or even sensible concept. During the 1973 Yom Kippur War, numerous battlefield photographs were Published showing Soviet BMPs whose turrets had been literally blown off. Some critics suggest that armies would be better advised to follow the Israeli example of the Merkava MBT end develop their tanks to carry some soldiers rather than to expend further resources on ICVs. Also, newer ICVs tend to rival tanks in size, weight, fuel consumption and cost but lag far behind in combat effectiveness.
Characteristics of modern ICVs are at Table2.
FIELD ARTILLERY
It was the employment of artillery that extended the lethality and destructiveness of the battlefield from 18th century onwards. During World War II, almost 60 percent of all battle casualties were casualties were caused by artillery fire. Major technological advances in mobility and munitions have occurred in recent years. Sophisticated guns, revolutionary types of ammunition and automated fire control systems with reliable digital communications, are being increasingly introduced into service and are leading to the most profound rethinking of tactics since world war II
Guns and Howitzers
Modern artillery guns are being designed o fire faster and farther, with greater efficiency. As well as to provide the cres protection against. Small arms fire and shell or bomb splinters. These guns are caable of good cross country performance. Short time into and out of action, high rate of fire and, in some cases, air transportability 155 mm and 152 mm calibers have crystallised as the ones most favoured by NATA and Warsaw pact countries, respectively for their towed and self-propelled (SP) medium artillery.
Towed 155 mm guns like FH-70 of UK-FRG-Italy and FH-77B of Sweden, are equipped with auxiliary propulsion units which enable the gun to travel short distances independently of its tractor, greatly reducing the time required to come into and out of action. Hydraulically assisted semi-automatic loading enables even these heavy guns to achieve burst rates of fire. FH-77B can fire a burst of six rounds in 20 seconds and has a sustained rate of fire of six rounds minute for 20 minutes. Sore guns are equipped with swing-back barrels which, in the travelling position, reduce the turning radius of the tractor and gun and enable the gun to occupy far lesser cargo space during air transportation. The SP guns mostly have 360 turret tra traverse, large ammunition stowage capabilities and mobility comparable with MBTs.
Table 3 gives comparative data of some selected guns and howitzers which are representative of their genre.
Rocket Artillery
Rocket artillery weapons systems offering rapid response, heavy volume of fire and long range fire support, with better fragmentation patterns than conventional gun shells, have a special place in modern artillery. The Warsaw Pact forces attach considerable importance to their rocket weapons systems like the EM21 GRAD (In Russian, Grad means “Hail”). The EM 21 is a truck-mounted multiple launcher with 40 122 mm tubes. One battery of BM 21s (8 launchers), can deliver 320 19.4Kg warheads on a target in merely 20 seconds. To achieve the same effect with conventional guns, 18 medium regiments would need to simultaneously fire one rounds per gun –a feat required deployment management wizardry and computer assisted coordination.
The new Multiple-Launch Rocket System(MLRS), recently developed jointly by the USA, UK, FRG and France, is a free flight, are weapons system. Its primary missions are counterfire and the suppression of enemy air defence weapon. The MLRS fires improved conventional sub-munitions (ICMs) as will as a scatterable mine warhead and has the potential to add an anti-armour terminally guided warhead and a binary warhead for chemical weapons.
Future long range surface to surface artillery rockets will extend the land forces area of influence deep into enemy territory, enabling the artillery to undertake interdiction tasks with more efficiency and a better assurance level than the air force. Rocket warheads carrying Durandel type runway denial munitions will be Able to disrupt operations at the enemy’s forward and intermediate tier airfields far more effectively and at a fraction of the cost of losing sophisticated modern aircraft. The entire gamut of counter-air operations will have to be reviewed in the near future.
Table 4 shows the characteristics of rocket artillery weapons systems in service and under development.
Spectacular Development in Ammunition
There have been truly astonishing developments in the field of ammunition – the ultimate weapon of artillery. Advances in metallur7y and explosives technology have led to the manufacture of new high explosive Shells made of “modern steels” with a composition B filling, which are 40 percent more lethal than normal shells. 155 -Am smoke shells have been designed with a burning time of six minutes and illuminating shells provide high intensity illumination for 50 to 60 seconds, against 20 to 30 seconds given by existing shells.
Ingenious methods have been devised to increase the range of artillery projectiles. Hollow base projectiles increase the volume of the combustion chamber and thus enable a larger propellant charge to be employed. Extended range full bore (ERFB) projectiles employ longitudinal NUBS along the body combined with a boat-shaped tail to reduce base drag and thereby increase the range with a purely ballistic solution. ERFB propellant with a base bleed unit (BBU) use a grain of solid propellant at the base which burns gradually and further reduces base drag. The 155 mm GC 45 gun-howitzer fires an ERFB projectile with a BBU to a maximum range of 39000 metres. Rocket assisted projectiles are fairly common and use a solid propellant motor to increase the range by 15 to 25 percent. Extended range sub-calibre projectiles are similar to APFSDS projectiles.
A new generation of carrier projectiles is fast entering with Western artilleries. Improved conventional munitions (ICM) shells contain 60 anti-personnel and anti-tank grenades. USA’s M449 (155 mm) projectile contains 60 anti-Personnel grenades and M483 projectile contains 64 dual-purpose grenades. Remote anti-armour mine system (RAAMS) projectiles developed in the USA contain nine anti-tank mines with variable self-destruct timings. Area denial artillery munitions (ADAM) carry 36 anti-personnel mines.
The copperhead cannon launched guided projectile (CLGP) has for the first time endowed indirect fire weapons systems with single round hard target kill capability. The 155 mm CLGP is terminally guided on to its target by a ground-based or airborne observer who uses a Laser target designator. The shell homes on to the reflected team with uncanny accuracy. The sense and destroy armour (SADARM) projectile is another US concept to produce an artillery launched, autonomous anti-tank weapon which has sub-munition being ejected from their carrier warheads over the target area in which they seek and destroy their own individual targets. The sensor on each sub-munition scans the target area during a parachute controlled descent. When the sensor detects and AFV in its field of view, the sub-munition fires on explosively formed projectile which strikes and penetrates the target on its top armour. Sub-munitions which miss, implant themselves in the ground to act as conventional anti-tank mines. Proved earlier for the 203 mm (8 inch) calibre, SADARM projectiles are now being developed for 155 mm guns and when the concept reaches the production and deployment stage, it could revolutionise anti-tank defence on the future battlefield.
Advanced indirect fire systems with “fire and forge capability, the ultimate in anti-tank defence, are under development. A projectile similar to SADARM is the smart, target activated fire and forget (STAFF) shell. This employs an antenna in its nose which measures the radio waves reflected from the metal of an AFV. STAFF is fired in close proximity of the target and is then guided automatically by an onboard computer.
Other projectiles under develop vent are chaff dispensers, artillery delivered sensors and expendable communications jammers. Anti-radiation projectiles are in the stage of proving trials. Beehive rounds, shells resembling a shotgun shell with thousands of small darts, are likely to be added to the inventory in the near future. Millimetre wave, infra-red, semi active Laser and radio-meter sensors have been found suitable for the guidance of artillery projectiles.
AIR DEFENCE ARTILLERY
The 1982 Falklands War brought out in stark reality the absurdity of the British General Staff’s thinking that each new technology automatically invalidates its predecessors -they had opted for portable and mobile surface to air missiles (SAMs} at the expense of discarding all-weather and fair-weather air defence guns, against which even the most sophisticated aircraft cannot employ any worthwhile counter-measures. All forms of missiles that home automatically on the target are inevitably vulnerable to jammers, decoys and other false sources that either lure the missile away or remove the source of honing signals. The back-up of SAMs by air defence guns, whose efficiency is dependent only on human skill, has again been recognised as inescapable.
The Warsaw Pact has a dense air defence network made up of long-range search radar units, jamming units and both fixed-site and mobile air defence weapons systems. Mobile units move with ground forces and consist of the shoulder-fired SAM-7 (Strella), the 23 mm quad–barrelled ZSU-23-4B (Schilka) and the twin-barrelled fair weather 23 mm gun (ZU-23). Also part of the ground forces protection units are the low-altitude SAM-6 (Kvadrat) SAM-8 (OSA-AK) and the SAM-4 (Ganef). Recently introduced weapons systems have comparatively far greater technological sophistication. SAM-9 (Gaskins) has a 3 to 8 km range and uses an infra-red seeker. SAM – 10 is said to have characteristics similar to those of the latest US Patriot, with a range of 64 km and an effective altitude of 30000 metres. Such a system would be extremely effective against cruise missiles and low flying strike aircraft. Other new Soviet air defence weapon include the SAM-11 using radar guidance and the SAM-13 using infra-red homing and sai to be comparable to the American Chaparral. A new portable weapon is SAM-14 which rivals the US Stinger and the British Blowpipe missiles.
NATO air defence systems have better guidance capabilities greater ECM resistance and, consequently, a higher kill ratio. The US designed Redeye portable missile is being replaced by the stinger and the very capable British Blowpipe. The US Vulcan fair-weather gun is being replaced by the newer DIVAD (Division Air Defence System). Low-altitude, mobile SAMs are the US Chaparral, French Crotale and British Rapier. The new US Patriot will replace Hawk and is designed to counter high-speed aircraft and missiles at all altitudes.
Trinity, a modern run system developed by Before of Sweden merits description in some detail. With its original 40mm calibre single barrel, Trinity can fire a burst of 10 individually aimed rounds in less than two seconds. Each round has a devastating proximity-fuzed warhead with snore than 1000 lethal pellets which form a computer designed compact group around the oncoming aircraft or missile, Even the precise details of fusing for each round are inserted by computer a split second before firing. “Bulls eye” accuracy is achieved by radar/optical sighting, Laser ranging, computerised meteorological input and extremely high muzzle velocity.
The inevitable result of such deadly low-level defences as Trinity and the highly accurate British Rapier SAM, is bound to be a renewal of interest in flight over 9000 metres (30000 feet), beyond the effective reach of these systems. At higher altitudes, the density of air defence weapons is considerably less and al the manual systems, which are usually free of counter measures, or eliminated.
Salient features of some representative air defence weapons systems are at Table 5.
NUCLEAR ARTILLERY
(TACTICAL NUCLEAR WEAPONS)
Nuclear Artillery in Service
In the late 1950s, faced with the Soviet Union’s 73ssive conventional power threatening Western Europe and with the technical ability to pack a nuclear warhead into a we noon the size of an artillery shell, the United States developed and deployed a whole range of battlefield nuclear weapons to deter a conventional attack rind to force the tactical dispersion of Soviet armour. Now the Warsaw Pact has caught up and produced a stalemate at the tactical level as well.
Guns of the calibre of 152 mm and above are capable of firing atomic projectiles. The M 422, 8-in (203) nuclear shell carries the W 33 warhead, using enriched uranium – 235 as its fissile material and has a yield of unto 2 – kilotons. It can he fired by the M 115 towed howitzer and the H 55, N 110 and A1-A2 SP howitzers at ranges unto 22 kilometres. The M 753 projectile, carrying the W 79 ER warhead with a yield of 0.7 kilotons, is likely to be introduced into service shortly. The 155 mm 14 785 nuclear shell carrying the w 82 warhead uses plutonium – 239 as its fissile material and has two yields – one sub – kiloton and the other 4 to 5 kiloton. This can be fired from the M 198 towed howitzers, the M 109 A1/A2 SP howitzer and all NATO 155 mm howitzers.
The US Field Artillery’s Lance missile is a dual – purpose tactical system designed for carrying either a 450 kilogram conventional high explosive warhead or a nuclear warhead with yield options from 1 to 100 – kilotons. Lance is launched from the M 752 amphibious tracked vehicle which normally carries three missiles and has a range between 72 and 120 kilometres. Pershing 1 A is another motile US missile with a range of 360 to 835 kilometres and a 60 to 400 kilotons warhead. This is being currently replaced with Pershing II which will carry a warhead of between 1 and 10 kilotons but have a range as much as 2415 kilometres. The new range will make the missile a tactical as well as a theatre nuclear weapon like the Soviet SS 20. These missiles are also referred to as Euro-Strategic. Soviet Artillery’s tactical nuclear missiles are based mainly on FROG 3 to 7 (Free Rocket Over Ground). FROG 7, the newest in the series, has a range of 70 kilometres and carries a warhead of 200-kilotons. The dual-purpose Scud series of missiles with ranges upto 450 kilometres are being replaced with SS – 23, Superscud. The FROG rockets are being replaced with SS 21 and SS 22 missiles with more sophisticated guidance and improved range.
NATO’s tacti.al nuclear stockpile in Europe includes 2250 atomic artillery shells, 180 Pershing IA, 90 Honest John (Rockets), 97 Lance and 700 Nike Hercules SAMs. France has 42 Pluton missiles with a range from 10 to 120 klometres and a warhead of 15 or 25 kilotons. NATO’s nuclear weapons are under ‘dual – key’ control. The warheads are under US control while the launchers or howitzers which fire them are under ‘host nation’ control. Also, the new neutron weapons are being stockpiled only in the continental US, instead of being forward- based in Europe, which makes far more tactical sense.
The general data of various nuclear artillery weapons systems in service are given in Table 6.
Enhanced Radiation Neutron Weapon
Enhanced radiation (BR) neutron weapons have been specifically developed as tactical battlefield weapons, fired from guns and missiles to destroy personnel inside hard military targets. Dose for dose, neutrons are more dangerous to the human body although they do not travel as far as gamma rays. Neutron radiation which lasts only about one or two seconds, can kill soldiers in hard shelters such as tanks at a greater distance then the overpressure created by the blast. As radiation decays rapidly with distance, it is only in smaller nuclear weapons that the destructive of fact of radiation is greater than that of blast and heat. Thus, when the target is a large AFV concentration, it is more profitable to employ ER weapons which cause minimum ‘collateral damage’. A one-kiloton ER weapon will produce a 3000 – rad dose inside a tank within a circle having a radius of 1 kilometre. A 10 – kiloton standard weapon would be required to Produce the same level of radiation. (An exposure of about 4000 rads leads to death in two to three days. Near ground zero, are the dosage would be 10 to 20 times greater, death would to instantaneous). It is for these reasons that the ERRE (enhanced radiation/reduced blast) neutron weapons have been developed.
A major controversy revolves around the use of neutron weapons. By treating neutron weapons as a special type of anti-armour technique, nuclear planners have risked blurring the distinction between nuclear and conventional warfare. In general, spokesmen talk as if “at neutron weapons and ordinary nuclear weapons were distinguishable in principle because they have difference in effect. Capability and objective are stressed more than the physical nature of the weapon. This itself runs contrary to one of the central tenets of flexible response linking the level of response to the degree of provocation – which was one of the initial justifications of neutron weapons.
BATTLEFIELD SURVEILLANCE AND TARGET ACQUISITION
A new generation of battlefield surveillance devices promise to extend a formation commander’s area of influence into the deeper tactical zone, bestowing on him the ability to penetrate the “shadow of the hill” and thereby fully exploit the Potential of the long range weapon systems available to him. Foliage Penetrating radar capable of detecting moving targets obscured by moderate amounts of tree lines or hedgerows, are under development. Radars which can detect stationary targets in addition to moving ones, are no longer a futuristic surveillance objective but reality. A Radar – Laser hybrid, combining Radar and Laser sensors, will provide all – weather surveillance target acquisition and target designation capabilities integrated into a single system. Future remotely Piloted vehicles (RPVs) will use a large number of surveillance techniques including Radars, low light level (TV (LLLTV), electro optical sensors and night vision devices (NVDs) The new family of far infra-red thermal imaging will be extremely effective because of its ability to penetrate camouflage to locate targets, yield longer detection ranges and be operational in near total darkness.
Information about enemy activities beyond a forward observers line-of-sight can also be obtained by unattended ground sensors (UGS). These devices are seismic, thermal, magnetic or acoustic. At persent, mostly thermal and seismic devices are in filed use. WI were used by the American forces in Vietnam with mixed results. It is now possible to produce devices which can discriminate between signals and report only those with military significance. Such devices placed at key points along likely routes of movement or exposed flanks, can be used for intelligence gathering in addition to targets acquisition. UGS are placed by aircraft, artillery shells or by hand through infiltration.
