As i read the 2008 errata i don't understand the supporting fire rule.
Does in the end of the first round if nobody was wipedout you can call for suppoer,what happen in the next round of assault?
Who can lend to the support?

The sequence as I understand it

See who is able to lend support (within 15cm of an enemy formation either attacking or defending).
Make all the attacks from the assaulting and defending formations.
If one side is wiped out give a blast marker to all those enemy formations who were in range to support in step 1.
If not, make all supporting fire attacks from all those still within 15cm of the enemy (their targets may have died).
Then see who has won and give blast marker to all those enemy formations who were in range to support in step 1.

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As others have said, the principles behind supporting fire have not changed. However, the whole Assault process has been changed slightly by resolving each stage of the assault before going on to the next, essentially to check whether the assault has ended prematurely or not.

The point to note is that now, support fire does not happen if the assault ends prematurely because the defense is wiped out or the attack stalls (the entire defending formation is dead or no attacking units left in 15 cms of a target unit respectively).

The main reason behind this is to close a loop-hole where a tiny sacrificial formation attacked (knowing it would be wiped out) in order to bring in a huge supporting formation that could not suffer any damage.

As TRC says, you should also note that "supporting" formations on the losing side get a BM even if they were not actually able to do anything for various reasons (including the premature end of the assault).

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Thanks guys