This is the board at start of turn two, with Crassus in the foreground, Romans the white-on-black counters.
Right away it became clear that each move would be important in such a chaotic situation, and that the order of events would greatly impact on the plans of each commander. Crassus began by using cavalry and light infantry to drive a wedge between the Parthian centre and its right wing. The light cavalry all-out-attacked from distance to score 2 hits on the Parthian centre but did not survive the counterattack.
On the Roman right both sides tried to force the other to advance first, but in the end it was Surena who charged into contact. Unfortunately, I made a rules error here; I momentarily forgot that cataphracts cannot move and attack in the same turn, so this was an illegal move.
On the Parthian right the light cavalry disperses to make it more difficult for the Roman centre and centre left to advance into contact with the mostly spent centre.
Observations: when commands are relatively plentiful, as they are in this scenario, there is incentive for players to do a higher proportion of single-unit moves than we might normally see. That said, there is a lot of space on the board in this scenario and there would not be the same opportunities for this in battles where the board is more densely populated.
(Board after turn 2)
The third turn saw the Romans get in the first move, which they used to attack with the heavy cavalry on the left. The turn proceeded with tit-for-tat attacks, culminating in Crassus Jr. rolling snake eyes while attempting a rally.
The Romans now had the semblance of a line but the right was entirely spent.
Observations: there perhaps needs to be provision for troops who wish to vacate a zone entirely to be able to move out all of their units in one go, even if it requires more than one phase to do so. Deciding whether to prioritize attacks over movement, and if so where, adds another interesting layer of decision making to the game.
(Board at end of turn 3)
The Romans had first move again this turn, which they used to get in another attack from the unfortunate Crassus Junior's zone. They scored another hit there before their right was eliminated. The Romans turned their centre to meet the threat from their collapsed right, while advancing on the centre left to try and get closer to the juicy targets in the Parthian centre.
The Romans now had only three zones with troops in them, so the Parthians could easily keep out of reach of the legions if they so wished, and could move individual units around to maximise morale attack advantages.
Observations: while you would think that having first move would confer a significant advantage, as the game wears on, the extra reaction ability that moving last brings - especially when there are several unanswered moves - seems to be very effective in its own right.
(Board at the end of turn 4)
It was at this point that I realised I'd made the error I mentioned earlier with the Parthian cataphracts, so I decided that there was no need to continue as the result would be devalued and that the things I'd wanted to test had been done so satisfactorily. It was also getting rather late by this point, so that was a factor too!
All in all, I thought alternate movement worked quite well. Playing against a live opponent there would be room for clever play and the chance to exert a bit of psychological pressure here and there with adroit manoeuvre. The problem of course is whether such clever play detracts from the simulation value.
As a final point, the board did not get cluttered; I used the provided 'attack made' markers to show which zones had already attacked, and when adjacent zones had both attacked I conserved said markers by placing a single marker across the borders of the two (or more) zones.