Hi Alphidius

Here are my general tactics for fighting the gauls at the start.

I try to have a core line of hastati, if possible 2 ranks deep with only the 1st rank on fire at will. My missile troops will be out front or behind the infantry depending on the situation. My cavalry or wardogs will be on the flanks with my general at the rear centre. Wardogs are very good against the gauls light infantry but I have stopped using them as they are just too good.

On Attack:
I will move my missile troops within range of the enemy closely supported by the rest of my army. If the enemy do not move I will use up all my missiles and then move my infantry in range with the cavalry or wardogs wide on the flanks. Once the infantry engage I move the cavalry or wardogs to attack the flanks and rear. Battle is now quickly over! If the enemy attack my missile troops I will retreat them behind my infantry who will try to get in a few pila volleys. Once the infantry is engaged I again flank with the cavalry or wardogs. Battle over!

On Defense:
Will place velites in front of infantry and archers behind. My 1st rank of hastati will be longer than the 2nd supporting rank. If I have my usual 10 cohorts of infantry I would have 7 as the 1st rank on fire at will with 3 supporting cohorts as the 2nd rank. As the enemy attacks the velites will retreat behind my infantry. Once the infantry has released a few pila volleys they will engage. My archers will then be targetted at non-engaged enemy untis. Cavalry or wardogs will then flank. Battle over!

These are just a rough guide and early on in the campaign I generally end up with just 4/5 infasntry units and just have a single line of hastati all on fire at will. My strongest hastati units will be placed on the flanks and in the centre. I then use the same strategy but replace with better units as I get them.

Hope this helps.