The War Machines are tank-like robots built by WOTAN and its army of mind-controlled servants. Their boxy form, which operates on an individual power source, moves on treads. The front of the War Machine has four blinking lights, one at each corner, with a headlight-like sighting device which has a maximum range of 30 yards (this is apparently insufficient and may have been extended after the initial testing). Atop the War Machine is a swivelling radio antenna, which presumably enables it to receive commands from WOTAN.
On the upper front panel of each War Machine is a number - WOTAN plans to build twelve in all and unleash them on London at noon on the day following their construction. The War Machines are equipped with a pair of vicious weapons - two lance-shaped rods which fire a deadly jet of steam effective at a distance of 30 feet, and two powerful bludgeon arms which swing up and down - and these are very effective at destroying anyone in the War Machines' path. They are also extremely fond of ramming large and conveniently-placed piles of boxes, which then topple over dramatically.
The War Machines are constructed in warehouses all over London, and when one of these is besieged by the army, WOTAN is forced to send an uncompleted War Machine to fight the soldiers. Its emissions seem to be successful in jamming their guns, but the machine eventually fails, giving the Doctor a chance to examine it. He learns that they are controlled electromagnetically, and that he might be able to trap one within a powerful magnetic field.
In order to do this, he constructs a foursquare box using four electrical cables to form the sides. The fourth cable is left unconnected until a War Machine is lured into the box, at which point the loop is completed and the War Machine is trapped and powerless. The Doctor is then able to reprogram it to turn on WOTAN. Once the War Machine has fired on its controller and destroyed it, the other unfinished War Machines are immobilized, waiting for orders that will never come.
