[an error occurred while processing this directive]

Real-life Ground Equipment

There are many types of equipment available to the foot soldier which don't fall under the category of small arms, artillery, or armour. While by no means a comprehensive listing, the following is a brief list of some important categories:


The concept of the grenade needs no explanation, since grenades have been a perennial fixture in action and war movies since long before most of us were born. However, while action movies may provide an introduction to the basic concept of grenades, they don't provide a realistic picture of their capabilities and limitations. Hand grenades can generally be thrown roughly 25-30 metres by the average soldier, so they are obviously designed to confine most of their destructive effects to a radius smaller than 25-30 metres. Some major types of grenade follow:

American M61 fragmentation grenadeFragmentation grenades: these grenades are designed to spray shrapnel around a wide area. Frag grenades generally have a kill radius of 5-7 metres, and a casualty radius of 15-20 metres, although these radii are not hard limits; individual fragments can be thrown hundreds of metres, so the user is advised to seek cover after throwing a frag grenade, even if he is well outside the casualty radius. Their structure is that of a small high explosive sphere surrounded by several metres of tightly wound steel wire. A cylindrical fuse (composed of a slow-burning combustible) goes into a hole through the centre of the sphere, and the entire assembly is encased in a metal shell. For reasons of safety, fuses are stored separately in the armoury, and issued separately to soldiers for subsequent assembly. When the grenades explode, the confined detonation produces an enormous overpressure which disintegrates the steel wire and shell. The resulting fragments are thrown outward at supersonic speed, perforating anything in their path. The "immediate action drill" upon detection of an imminent frag grenade explosion is to dive to the floor away from it, since the chance of being hit by shrapnel varies directly with the surface area you present to the explosion, and it also obeys the inverse square law with respect to distance.

An interesting fact about the fragmentation grenade is that it actually produces a rather small explosion, without the enormous shockwave or fireball that normally accompanies a grenade explosion in an action movie. Structural damage to the surrounding area is not significant unless flammables are present. The reason for this is that a frag grenade is designed to transfer as much of its chemical potential energy as possible into the kinetic energy of its shrapnel, rather than producing a powerful localized shockwave and fireball. Therefore, a frag grenade explosion in a typical room will leave it looking much the way it was before. However, a close inspection of the room would reveal countless jagged metal fragments embedded in the walls, and any men in the room would be dead. Moreover, even men in adjacent rooms might be dead or injured, depending on their proximity and the construction materials used. The velocity of the fragments is such that they will easily penetrate deeply into all normal building materials, so drywall and even wooden doors would not provide enough protection. Unless the walls and doors are made out of concrete and steel, your best chance is to put as much distance between yourself and the grenade before it explodes, rather than counting on a door or a wall to protect you. The fragments are also red-hot, and can easily ignite widespread fires, thus causing a potential for serious risk even if the explosion itself doesn't kill you.

Smoke grenades: these are designed to produce a thick cloud of smoke by igniting a slow-burning combustible that "burns dirty", hence the opaque combustion byproducts and low temperatures. The structure is that of a cylinder filled with the aforementioned combustible, and since the burn is so inefficient, the cylindrical canister is not destroyed by the process. The purpose of a smoke grenade is simply to deny sight to the enemy in specific areas, either to cover your movements or to distract and deceive (eg. three clouds of smoke splits his fire and concentration more than one).

Tanks usually have special smoke canisters which deploy phosphorous smoke grenades. The importance of the phosphorous is that it is opaque to infrared, just as normal smoke is opaque to visible light. This provides cover from thermal imaging sights, which is crucial since tanks are normally equipped with such sights, and smoke canisters would be of little use if enemy tanks could see right through it. However, since the smoke produced by burning phosphorous is highly toxic, it is not normally used by foot soldiers. Tanks may have integrated NBC protection, but foot soldiers generally do not.

One popular misconception propagated by action movies is that a soldier will detonate a smoke grenade near himself by dropping it, throwing it a short distance, or perhaps even hurling it to the ground at his feet (a popular trick in ninja movies). This is highly unrealistic; a smoke cloud in your immediate vicinity will obscure your vision in all directions, while obscuring almost none of your enemy's vision. He may not be able to pinpoint you inside the cloud, but he can see the entire landscape except for the cloud, while your vision may be largely obscured in all directions. This is counterproductive, to say the least. The proper way to deploy a smoke grenade is to try to ignite it as close to the enemy as possible, so that it obscures the largest possible viewing arc from his perspective, not yours. Furthermore, the smoke, while not as toxic as that produced by burning phosphorous, is nevertheless harmful and should be avoided.

White phosphorous grenades: these grenades are filled with (surprise!) white phosphorous, thus leading to the nickname "WP grenades" or "Willie Petes". The American M15 grenade contains about 15 ounces, along with a small bursting charge which ignites the phosphorous and scatters it over a 17 metre radius. The phosphorous burns for about 60 seconds at more than 2000 K (which is higher than the melting point of steel), and it will naturally ignite every flammable object in the area. The burning particles can also embed themselves into human flesh, where they will continue to burn, causing excruciating pain and sinking deeper into the victim's body. Water can only provide temporary relief, as the particles will spontaneously re-ignite the moment they dry. They must therefore be carefully picked out before re-ignition or doused with copper sulphate, which will prevent re-ignition. This type of grenade will cause severe, possibly even fatal injuries to enemy soldiers, and worse yet, its smoke is highly toxic and can also injure or kill. WP grenades are generally used to clear rooms or trenches or other confined areas where it is unlikely that shifting winds will blow the resulting smoke back into your face.

Stun/flashbang grenades: these grenades are generally used for anti-terrorist and riot control purposes. They use magnesium powder (flash) and mercury fulminate (bang) filler. The magnesium powder produces a blinding light while the mercury fulminate produces a deafening percussive noise. The combination produces sensory overload that renders him unable to function for roughly one half-minute, and leaves him seriously disoriented for another half-minute. Some versions are even capable of multiple bursts, for a more prolonged impact. This type of grenade will become more important in the sort of low-level warfare that may typify future conflicts; in Somalia, Rangers and Delta Force commandos used flash-bang grenades to scatter non-combatants who were inadvertently or deliberately providing cover for enemy soldiers.

Gas grenades: gas grenades are generally restricted items (except for the tear gas grenades used by the police). Due to humanitarian reasons, they are being gradually phased out of western armies. However, this does not preclude their use on the battlefield, since there are many armies in the world for whom humanitarian concerns are irrelevant.

Thermate grenades: these special-purpose grenades are (obviously) filled with a substance called thermate. Thermate is a powdered mixture of 1 part barium nitrate, 2 parts aluminum, and 3 parts iron oxide (rust). The aluminum and iron oxide particles are known as thermite, and when ignited by a very hot-burning fuse substance such as magnesium, the resulting incendiary reaction can easily melt steel. The burning liquid metal produced by the reaction has an accelerated heating/corrosion effect, and an M14 thermate grenade is said to be capable of burning a hole through a ½-inch thick steel plate. The addition of barium nitrate distinguishes thermate from thermite, and it allows the mixture to burn even when submerged underwater. Unlike the anti-personnel WP grenades, thermate grenades can be used to damage vehicles, small buildings, stored munitions, etc. The burning metal welds parts together, burns holes through plate, and distorts structural components. However, the area of destruction is quite small, so these grenades are not very widely used.

Concussion grenades: thanks to the movies, this rarely used device is actually the archetypal grenade as far as John Q. Public is concerned. Concussion grenades are filled with high explosive, and upon detonation, they produce a powerful localized overpressure shockwave that can cause serious structural damage to adjacent objects. In movies, a concussion grenade is usually used as an anti-personnel weapon; a grenade will land near our hero's feet, he will run for his life, and the explosion will occur while he's still only 2-3 metres away. He will be hurled into the air by the force of the blast, and perhaps slightly wounded, but of course, he'll still be able to defeat an entire army afterwards. However, in reality, our action hero would have been punctured with numerous pieces of shrapnel because his enemies would have thrown a frag grenade, not a concussion grenade. A concussion grenade's casualty radius in open air is a mere 2 metres (as opposed to 15-20 metres for a frag grenade), so it's not very effective as an anti-personel weapon in most circumstances, and it's really more suited to demolition work. It is for these reasons that despite their prominence in action movies, concussion grenades are not often carried by the infantryman.

Note that while the term "grenade" is generally assumed to refer to hand grenades, it is actually not that restrictive. It can also refer to the spin-stabilized grenades fired from grenade launchers such as the American M203 (which is typically mounted to M16 assault rifles or M4 carbines), or rocket propelled grenades such as the Soviet RPG-7 (which usually uses HE or HEAT ammunition), or rifle grenades. Rifle grenades are not very well known by the public because they are never seen in action movies, unlike hand grenades, grenade launchers, or RPGs. They are long, cylindrical grenades which are designed to fit over the end of an assault rifle or carbine. You simply slip the grenade over the end of the barrel, and then you shoot an ordinary bullet. A "bullet trap" inside the grenade catches the bullet and transfers most of its kinetic energy into the grenade, which is then launched quite accurately, to a distance of 100-200 metres. Rifle grenades haven't been used by the American army since WW2 (hence their invisibility in action movies), but they are still used by numerous other armies around the world. Grenades of this type are larger and more powerful than the 40mm grenades used in grenade launchers such as the American M203, but their accuracy and range are inferior. The reason for the American army's lack of rifle grenades are unclear; there are tactical situations in which an M203 firing spin-stabilized 40mm grenades with 350 metre ranges would be more appropriate, but there are also situations in which a powerful rifle grenade with half that range would be more appropriate.


Flamethrowers generally have greater psychological impact than tactical value, and can be considered a terror weapon for most intents and purposes. They are heavy, their range is limited, and if the backpack fuel tanks are hit by enemy fire, the user and any squad-mates in his immediate vicinity can be burned alive by his own weapon. Since flamethrower use often results in the wholesale destruction of buildings, it is not suitable for urbanized environments. They were once used to clear out confined spaces such as bunkers and tunnels, or to completely destroy buildings in urbanized environments (particularly when mounted on vehicles such as light tanks, where they don't suffer from the same drawbacks as infantry flamethrowers). However, mortars and WP grenades have made the flamethrower largely redundant in modern armies. As a further disincentive, they have also been banned for humanitarian reasons.

Anti-Tank Weapons

The M84 Carl Gustav recoilless anti-tank gunA heavily armoured main battle tank may be a fearsome sight, but it is not invulnerable. There are two basic varieties of anti-tank weapon: recoilless guns and guided missiles. An example of the former would be Sweden's "Carl Gustav" M2-550 84mm shoulder-fired recoilless gun, which is classified as a "medium anti-armour weapon". It requires two men to operate: one to fire and one to load, and after firing a shot, it can be ready for action again in around 10 seconds. It has a maximum effective range of roughly 700 metres (against stationary targets), and although one might not intuitively expect much firepower from a shoulder-fired gun, its shaped-charge HEAT round is easily capable of penetrating foot-thick armour. Although it was primarily designed as an anti-tank gun, it can also be used to support infantry by firing smoke, illumination, or HE shrapnel rounds with an effective range in excess of 1 kilometre. The never-ending war between weapons and armour continues to ratchet upwards, and special rocket-assisted HEAT rounds are also available for use against newer forms of composite armour. They have reduced range (300 metres), but they can punch through an astounding 35 inches of armour!

Anti-tank missiles are much more expensive, but they have the benefit of longer ranges. The Euromissile HOT is a heavy spin-stabilized missile which is designed to be fired from vehicles or helicopters, and which is said to be capable of penetrating the armour of all known MBTs at this time. It has an effective range in excess of 4 kilometres, and it can penetrate more than 30 inches of armour. The American TOW is a similar missile, again meant to be fired from a vehicle. Missiles like this are often mounted on specialized vehicles called "tank destroyers", which are essentially light armoured fighting vehicles with missile racks on top. They are generally wire-guided, with a human operator controlling the missile through some sort of manual reticle aiming system. "Fire and forget" missiles are the next logical development, but they come accompanied with a prohibitive increase in cost.

One thing to keep in mind when discussing these weapons is that armour penetration figures are for a direct hit at right-angles to the surface. A glancing blow is nowhere near as effective, and tank armour is sloped for precisely that reason. However, this caveat doesn't apply to anti-tank missiles launched from helicopters, for which the sloped armour is actually counter-productive. Another problem with the armour penetration figures is that they are based on homogeneous steel armour plate. The nature of fracture mechanics is that homogeneous metals are weaker than metals containing discontinuities, hence the usefulness of laminate armour. Alternating hard and soft layers of metal, or even dissimilar materials such as ductile metal layered with hard ceramic can severely impede crack propagation. Layers of refractory ceramics would also have excellent thermal resistance (that's why they make blast furnaces out of them), which would be a factor in reducing the damage from the liquid-metal jet of a shaped charge. It is a common misconception that purity is a good thing (in both genetics and materials), when in fact, the exact opposite is true: purity is bad. A pure metal is weaker than an alloy based on that metal, a perfect crystal lattice is weaker than a disrupted microstructure full of impurities, and a homogeneous piece of metal is weaker than a series of dissimilar layers. The Japanese understood this centuries ago (as evidenced by their folded-metal sword making techniques), and although the exact composition of modern armour is not widely published, it seems a sure bet that it takes advantage of this principle.

In short, anti-tank weapons can be deadly opponents for a tank, and perhaps even an MBT, but they are not without their own weaknesses. Wire-guided missiles require an element of skill on the part of the operator and their effectiveness can therefore be mitigated by smoke discharge or even return fire, since it will distract the operator from his task. Recoilless guns require no such attention on the part of the operator, but they are only effective at short ranges. In both cases, armour penetration is highly dependent on how and where they strike the tank. Therefore, tanks still enjoy the advantage in environments where their superior firepower and range can be exercised to their full effect, such as the flat deserts of Saudi Arabia or the broad plains of Northern France. However, where there is sufficient cover or uneven terrain to permit close-range infantry attacks, even the most heavily armoured tanks can suffer at the hands of anti-tank weapons.

Anti-Aircraft Weapons

A century ago, the infantryman had nothing to fear from the air. His enemy was on the ground or at sea, and the only time he looked to the skies was in prayer before battle. Today, the situation has changed quite drastically. Aircraft roam far and wide over the battlefield, bringing reconnaissance data to the enemy or death to the foot soldier, particularly in open terrain. Weapons designed for use against comparatively slow-moving infantry or ground vehicles are useless against aircraft, so it has become necessary for the world's armies to design weapons which will bring those aircraft down.

The Swiss Skyshield 35 Revolver gunAs with anti-tank weapons, there are two classes: guns and missiles. There is some debate as to whether these categories are truly complementary, as opposed to being a transition from one technology to another. In WW2, air defense was exclusively based on guns (the infamous German 88mm AA guns being an obvious example). However, aircraft are not like tanks; they are too fast, too small, and too distant to hit directly. However, their lack of armour makes them easy to damage or destroy, so AA gunnery became like artillery, and used proximity-fused fragmentation projectiles.

However, at long range, the AA gun had little chance of hitting an aircraft, even with shrapnel from a proximity-fused fragmentation projectile. Massed AA guns were required in order to put up an "umbrella of steel", accomplishing through sheer volume and density of fire what they could not achieve otherwise. Luckily for the ground army, the SAM (surface to air missile) was eventually invented. Guided missile systems such as the British Rapier (pictured below, left) can hit aircraft up to three kilometres up, and it uses laser, radar, or optical guidance in order to correct its trajectory en route to the target. Much larger SAMs also exist, such as the British Bloodhound which has a range of more than eighty kilometres. The lethality of the SAM meant that long-range, high-calibre AA guns were no longer necessary, but small-calibre, high firing-rate low-level air defense guns still had a role. They almost died out in the 1960s because of the difficulty of traversing quickly enough to hit increasingly nimble aircraft, but the advent of robotics solved this problem by tying electromechanical control systems to computers and sophisticated imaging systems (more on this later).

The British Rapier anti-aircraft missile systemNevertheless, missiles continued to evolve, and shoulder-launched AA missiles such as the American Stinger, the British Blowpipe, and the Soviet SA-7 are arguably capable of replacing AA guns even for low-altitude targets. However, while their cost per firing is much lower than that of larger SAMs, they are still more costly than shells from an AA gun, so a modern air defense is still largely based on SAMs for high-level defense and guns for low-level defense. Furthermore, AA guns have an added element of dual-role versatility, since the world's militaries haven't forgotten the infamous trick Rommel pulled with his 88's on the sands of North Africa. Some AA guns like the 20mm Israeli TCM-20 can elevate from 90° to -10° so they can fire at infantry or ground vehicles, thus becoming an infantry support weapon. Some AA guns are even equipped with both proximity-fused fragmentation shells and armour-piercing sabot rounds, to kill not only ground-attack aircraft, but also infantry and light armoured vehicles. Since a single-shot, single-hit probability is near-zero, these guns typically have fairly high rates of fire; the Swiss Skyshield 35 (pictured up, right) has a maximum fire rate of 1000 rounds per minute.

As an aside, the technical reasons for the limitations of AA guns lie in the limitations of their electromechanical control systems. The science of robotics is not as simple as some would have you believe; it isn't a simple matter of the computer telling the gun where to point. Even if the computer has an accurate target lock, and provides the perfect co-ordinates for the controller to traverse and elevate the gun to a certain point, the fun has not yet begun. The controller must feed power to motors which start moving the gun in the right direction. But the gun doesn't move to the right position by magic; it must accelerate, reach its maximum speed, and then decelerate as it approaches the target position. This takes time, and that's where the compromises and trade-offs begin. One way to reduce rise time (the time required to reach the target position) is to reduce its inertia by making the gun lighter, but this forces you to use smaller ammunition, thus sacrificing firepower. Another way to reduce rise time is to keep the heavy barrel but increase the motor power, but this increases the size and cost of the machine, and it also tends to increase the settling time (the time required for the gun to "settle down", or stop oscillating, once it reaches the target). You could address the settling time problem by using stronger damping (think of the shock absorbers on a car), but this increases the resistance to movement, thus requiring even more motor power. There is a delicate balance to be reached, and many layers of complexity which most laypeople are completely unaware of.

Land Mines

There are an enormous variety of land mines made around the world. However, there are certain generalizations we can make. Mines are generally used to deny area to the enemy. They can be deployed by hand or by vehicles known as minelayers. They are also the subject of intense political controversy and there are numerous activists who are actively trying to ban them completely. However, the repugnant civilian casualties caused by land mines are the result of indiscriminate land mine use rather than the inherent nature of land mines themselves. Armies which use them irresponsibly (eg. the Soviet army in Afghanistan) will leave a civilian death toll in their wake, but armies which use them responsibly (by tracking, logging, and eventually clearing their minefields) will not. A far-reaching ban would not be obeyed by the sort of armies which use them irresponsibly, so it seems pointless and counterproductive. Fortunately, modern land mines are beginning to incorporate self-destructing delay timers so that they don't need to be actively cleared, thus resolving some of this conflict. However, the controversy is likely to continue for a long time despite this development. A comprehensive listing of land mine designs is far beyond the scope of this document, but land mines generally fall into two groups: anti-personnel and anti-tank.

Anti-personnel mines: AP mines are generally very small, flat or cylindrical, and easily concealed (for obvious reasons). They contain only a tiny amount of explosive (perhaps an ounce), and they are designed not to kill, but rather, to main or mutilate the target. They are designed so that foot pressure will detonate them (a shotgun shell buried on top of a nail would qualify as an AP mine). A typical cylindrical AP mine will produce a highly vertical blast that causes such trauma to the victim's leg that it will often have to be amputated at the knee. A typical flat AP mine will produce a more dispersed blast that rips the target's foot to shreds, thus necessitating the amputation of the foot. AP mines are generally deployed to deny crucial areas to the enemy (such as your flanks), to push him into preselected fire zones. They will also be deployed in front of a defense line, to disrupt their momentum if they are on the verge of overrunning your position. They can be laid by hand, or distributed by systems such as cluster bombs or mine-laying artillery projectiles.

Anti-tank mines: AT mines are quite large, and resemble the mental picture most people have of land mines. They contain a much larger charge than AP mines, and they are designed around a shaped charge, to improve their effectiveness against armour. They can be activated by ground pressure (like AP mines) or by electromagnetic proximity sensors. They are generally deployed by specialized vehicles along likely routes of enemy vehicle travel and to the front of defensive positions, although like AP mines, they can also be deployed from delivery systems such as cluster bombs or specialized artillery projectiles.

Minefield placement is neither random or inconsequential, and is an integral part of any planned defense of a position. There is a great deal of training involved, and minefields will only be truly effective if you can monitor them and put fire on them if necessary, otherwise the enemy will be able to clear them and then attack from an unexpected direction. An army without mines wouldn't be able to effectively defend a position without enormous resources; they would have to be able to put heavy anti-personnel fire and anti-tank fire on an attacker approaching from any direction.

Body Armour

Body armour comes in two varieties: fragment/knife-proof vests and bulletproof vests. In both cases, they use a mixture of kevlar and trauma shield (the kevlar stops the penetration, while the trauma shield dissipates the impact), as well as a flame retardant layer to protect from blast heat. Bulletproof vests come in various strengths, some of which are actually capable of stopping rifle rounds at 50 metres. Body armour also performs a secondary function of "holding your insides inside", so it is often strapped tightly around the body. However, bulletproof vests are no panacea. Concentrated high-calibre fire will defeat them, and even a successfully blocked impact will often leave the victim wounded and seriously disoriented or perhaps even incapacitated for some time afterwards. And of course, they only cover your torso, not your entire body.

NBC Protection

Soldier using a special drinking bottle with an Avon FM12 NBC respiratorThe NBC (nuclear, biological, chemical) protection suit is much more complex than body armour. While body armour is designed to stop high velocity projectiles striking the wearer's torso, NBC suits must stop even the smallest particle of radioactive fallout, biological agent, or chemical weaponry from reaching any part of the wearer's body. Moreover, they must withstand the rigours of combat, unlike the delicate yellow suits worn by radiation workers and "hazmat" (hazardous material) teams.

The NBC suit is composed of several components: gloves, overboots, a facelet, trousers, a jacket, a respirator, and a specialized drinking bottle designed for fluid transfer without contamination (soldiers do need to drink, after all). The soldier must put on each piece in the correct order and following very specific instructions, or it will not function properly. The entire system is worn outside of a normal combat uniform. An example is depicted at right, with a soldier using a specialized drinking bottle in conjunction with a respirator. You can see the size of the lenses, which permit a very wide field of vision, and you can also see the size of the filter/scrubber, which permits high air flow. The bottle uses valves and positive pressure to deliver water to a specialized receptacle in the respirator without exposing the fluid to the environment at any time.

The respirator is the most important part, as it protects the face eyes, nose, throat, lungs, and face. Its design determines how well the wearer will see, breathe, and communicate. Therefore, it must have good visibility (ensured by large, convex lenses and a mounting point for extra, corrective lenses), high airflow filtration and scrubber systems, and a system for efficiently transmitting sound to the outside world. Modern respirators use floating plates for communication; they oscillate in response to internal soundwaves and transmit them to the outside, in a slightly distorted but still recognizable fashion for direct and/or radio communications.

The suit itself is also important, since the wearer must be able to do a belly crawl over broken terrain without tearing holes in it. Since no material is indestructible, designers deal with this problem by building the suit out of several layers (including a filter layer, of course), with staggered seams. The material is very rough to the touch, which increases surface area and therefore dilutes the radiological, biological, or chemical agent that will reach the soldiers's skin.

One of the problems with this system is its very specialization. A soldier must be informed ahead of time that NBC agents may be present, and then he must put on the suit. Therefore, most soldiers would be unable to deal with a surprise deployment of chemical or biological weapons. There are also endurance concerns; not only is the suit fragile, but the soldier himself will have a measurably elevated body temperature while wearing it. This will cut down on his stamina and endurance. It also doesn't qualify as body armour, and the use of a bulletproof vest on top of the suit would only exacerbate the heat problem. Some possible long-term future solutions to this problem include ideas such as a single body-suit which consists of an insulating inner layer, a gel-like filter layer, and an active cooling system. An armoured suit would go around this system, and an integrated respirator/battle helmet would be incorporated into the design, with electronic combat aids such as two-way voice and data communications, thermal and night-sight imaging systems, etc. If such a suit could be made light enough and comfortable enough, it could combine the functions of body armour and NBC protection into a suit which could be worn full-time, so that soldiers can maintain a permanent state of NBC readiness along with bullet and shrapnel resistance regardless of duty or posting. Of course, as an observant reader, you may notice that this scheme sounds remarkably similar to a white armour suit we've seen in certain science fiction films ...

Cool toys. Let's see what toys the Empire has!

Valid HTML 4.01!Valid CSS!This website is owned and maintained by Michael Wong
This site is not affiliated with Lucasfilm or Paramount
All associated materials are used under "Fair Use" provisions of copyright law.
All original content by Michael Wong is copyrighted © 1998,2004.
Click here to go to the main page