A War Machine is considered to be a single model with a single set of characteristics, defined as the following:
Toughness Use the machine’s Toughness against ranged attacks and crew’s Toughness against Close Combat attacks.
Wounds Use the machine’s Wounds.
Other characteristics and Armour and Saves Use the crew's Characteristics, Armour and other Saves.
War Machines have separate profiles for the machine and its crew members. Use the machine's Wound Characteristic in all cases. Use the machine's Toughness against ranged attacks. Use the crew's Characteristics for all other purposes. War Machines automatically fail any Characteristic tests except Leadership tests and cannot march or declare charges. If a War Machine fails a Panic Test, instead of fleeing it cannot shoot in its next Shooting Phase. When the model reaches zero Wounds, remove all parts of the combined model as a casualty. Characters can never join units of War Machines. When a unit charges a War Machine, follow the same rules as for normal Charge Moves, except that the charging unit can move into base contact anywhere (since all War Machines have round bases and thus don't have facings). War Machines, and units Engaged in combat with them, cannot make combat reforms. When fighting a War Machine in combat, do not allocate attacks as normal. Instead, at the start of each Round of Combat choose up to 6 models that are not in base contact with other enemies to fight (you must choose as many as possible). Chariots, Monstrous Cavalry, Monstrous Infantry and Monstrous Beasts count as 3 models each, while Monsters and Ridden Monsters count as 6 models each. The chosen models may then attack the War Machine as if they were in base contact, but no other attack can be directed at it, nor can the War Machine attack models outside the chosen party. Casualties among the chosen models are removed from the back of the unit as normal. Therefore if R&F models die before striking, the chosen party size does not reduce in size. Break tests are taken as normal. War Machines that break from combat are automatically destroyed.