I recently had a situation where my flank march was opposed by larger enemy flank march and subsequently driven back into my half of the table. Enemy arrived behind causing my nearest elements to flee. Some of my commnd were Irregular Blade (F) and on my next bound became impetuous. At this point the impetuous blades had no other enemy in sight due to a large hill blocking line of sight to the opponents' other troops. The enemy behind my blades being the only enemy they were aware of. The point which caused argument was that despite being impetuous they could not turn and attack the enemy behind them but had nowhere else to go.
What should happen, the rules do not appear to directly cover this situ. If the impetuous blades could not turn then how do they advance?? If they move away from the enemy behind them then this seems illogical as impetuous troops are then retreating from the enemy???