On any battlefield, there are places where conventional vehicles cannot go: built-up areas, dense forests, narrow tunnels, and so on. For this reason, many armies use vehicles that are propelled by two, or sometimes more, mechanical legs. These vehicles are usually capable of carrying as many weapon systems as a tank can on a significantly smaller and lighter chassis. They combine the armoured might of a tank with the manoeuvrability of an infantryman. In general, these vehicles have a single crewman. Space Marine Dreadnoughts, however, are more than simply a one-man vehicle. They contain the mortally wounded remains of great Space Marine heroes, becoming mausoleum and war machine all in one. It is considered the greatest honour for a Space Marine to be incarcerated into one of these ancient machines so that they may continue to serve the Emperor. The Eldar Wraithlord on the other hand does not have any crew at all. It is 'piloted' instead by a spirit stone containing the vital essence of a dead Eldar warrior.
Because of their manoeuvrability, lighter walkers are often used as recon vehicles. The Imperial Guard Sentinel and the Eldar War Walker are both designed with this role very much in mind. Dreadnoughts on the other hand, especially those created by the Orks, tend to be used as shock assault vehicles, striding into battle alongside their infantry and spearheading assaults.
The walker category also includes some war machines that use anti-gravitic engines such as the Dark Eldar Talos. Although not literally a walker, the performance of these vehicles' mirrors walker characteristics more closely than it does that of skimmers.
Designer's Note: This last clarification has been introduced to thwart those players who have tried to convince their unfortunate opponents that because a Talos utilises gravitic technology they need a 6 to hit it in close combat. They don't – the Talos floats rather than walks, but in all important game aspects it should be treated as a walker.
Including vehicles that have legs instead of tracks or wheels, the most common walkers are the huge war machines called Dreadnoughts. Walkers move like infantry so they can move up to 6" in the Movement phase and then charge up to 6" in the Assault phase if the enemy are within 6". Difficult terrain affects walkers just as it does infantry. Walkers moving into, out of or through difficult terrain have to roll 2D6 and use the highest result as the maximum distance they may move that turn.
Having sophisticated weapon systems that are fully integrated with their crew, Walkers can engage targets on the move more easily than other vehicles. This means they can always fire two weapons (one from each side/arm) regardless of whether they've moved or not. Walkers who do not move can fire all their weapons. Walkers make no distinction between main weapons and defensive weapons.