War engines in close combat
You may move your War Engine units in the Assault phase, and you may make charge moves with them if you wish. This does not affect the War Engine unit’s ability to shoot in the Shooting phase in any way; it always fires at full effect.
War Engine units have a comparatively high Assault value, as you will see on their data sheets. Lesser units can and must 'gang up' on a War Engine if they are to defeat it in close combat.
The maximum number of units that you may place in base contact with a War Engine unit is equal to the number of its initial Damage Capacity value. 
War engines can also do a lot more damage in close combat than regular units.
Roll a number of dice to hit equal to half the current Damage Capacity of the War Engine unit (round up).
As normal, you can allocate hits to any enemy units that are in base contact with any of your units in the close combat. 
For each regular unit that you have in base contact with an enemy War Engine, roll a single hit die as normal.
Ignore power fields and void shields for any hits that you score in close combat — they damage the War Engine directly. Roll for critical damage as normal.
When you add up Assault values for a War Engine detachment that is in close combat, do not add +1 for 'supporting fire' from each unit in the detachment that is within 15 cm of the enemy but not in base contact. Instead, add a number equal to half the current Damage Capacity of each such War Engine unit. 
To be clear, such units may still also support other detachments as we explain at War engines in support of close combats.
[TODO: Need a suitable graphic.]
Your Ork Great Gargant is in close combat with some Space Marine infantry.
It is undamaged, so its current Damage Capacity value is
This means that you roll nine dice to hit the Space Marine units.
Your opponent may still only roll a number of dice equal to the number of Space Marine units that are in base contact — four dice, in this case.