In Summary, you must attack what you are in base to base with regardless of which unit it is and when it assualted (remember that Independent Characters are considered a seperate unit in assault). Support attacks can be allocated to any legal target regardless of when they assualted.
Per latest FAQ:
Page 41 – Multiple Combats, Attacking.
A third bullet point should be added, as follows:
• Models that at the beginning of the combat (before
any model attacked) were engaged with more than
one enemy unit, but were in base contact with just one
of the enemy units, must attack that unit.
released Jan. 2012
- Hi my name is Chris, and yes, I'm talking smack with my unpainted Tau army.
- Math Marines: The Sons of Euclid
: Cause everyone knows we're Pi-M-P. π