You really have to prioritize taking Rome down. Ally with Etrusca, and anyone else on the Italian peninsula. Land your armies in Etrusca before declaring war. After you win, take Latium from them, this is where all their accepted pops live. The next war against them should be alot easier.

Try elephants levies on the flanks ;⁠)

Strategic Engagement and Containment

Box Rome in, prioritize taking Latium, ally with Etrusca, secure sardinia, corsica, and sicily before fighting them if you can. Basically rob them of easy expansions and crush them before they boom up.

Depends on where you are but as massalia or a nation in greece just out pace their navy. Step 2 is make sure to have a mountainous region such as the west Alps or the mountains in northern Macedonia and southern illyria with a bunch of forts in mountain provinces to tie them up and hit their stacks with concentrated forces of levies and mercy to slowly whittle them done. Step 3 is once the majority of their forces are tied up in your forts far from their capital I send my navy with my capital stack to sack all of the major population centers around rome and usually by that point you have free rain to sack a lot of Italy.

In previous plays ive done as carthage i went for them very early AND time it for when theyre already in a war. Gone straight for rome.

In my current playthrough i was far out so didnt encounter until quite late. In the first war i took southern italy and then just build catles all over it. Every war since theyve piled into italy and the forts have slowed them down while my armies take their stuff in africa or the illyrian area.

Also a tactic i use is get mercenaries from the middle of my empire and bring them up. Once theyve been wiped out i get the next lot of mercenaries which are much closer to the front lines.

Again always/only declare war if theyre already in 1 so their armies will be delayed. And fortify the crap out of a 1 border region so u can focus in other areas. Romes navy is crazy big in my game so ive just avoided it and used my navy as a glorified ferry.

It depends on many factors. How to control victory on the battlefield:

1. Traditions. Rome has very small roster of units levies provide. And technologies boost therefore, larger portion of the army when they accept the new tradition. Carthage on other side has much wider roster and the strogest unit Elephants is quite seldom in Vanilla. In Invictus, the situation is better since levies are more concentrated and HI is not such universal like in Vanilla. From your side try to empower the most common units to be more effective on average, not few the strongest if you use levies.
2. Positioning. Rome in both versions positions HI in the center, ensure that your first row will be units which will counter HI the best. If it is not assigned which may be the case in vanilla then you are on the mercy of random and your HI will be weaker than Roman.
3. Terrain. Romans have access to tradition increasing damage on the hills and you on the plane. The try not to fight them on the hills. They, at leaast, have no adv on the plain.
4. Pantheon. Use omens to boost your morale/disc.
5. Tech. Ensure you have good amount of disc and morale from techs to fight on the same lvl like Rome
6. Governors Martial, if your governor has martial 2 with 55k tropps when the enemy has 9 with 26k them you normally has no chance to win. Enemy will inflict much more damage on average. Replace governors with something better or if it is impossible then use mercs as Martial providers, game always assign the char with highest martial as a combat leader.
7. ideas: Use ideas to increase morale, disc even if you lose a bonus from government type when winning battles matters.
8. Tactics. AI commonly uses some random tactic which is good for his current current setup depending on his assumtion what you can pick. Then just assume what it can pick and try to counter it or is there are too many self excluding option then jsut pick something when you both wont get any advantage. Tactics affect damage if they chosen poorly.

I hope, it is not to much XD, but you can control how bt will happen in your favor with so many options!

I’d say try and take them down early, you start off in a stronger position but Rome expands really quick.

If you’ve left it too long and you’re more evenly matched then yes, utilise the navy, find their navy first and keep it in port, then blockade them. Try and get legions so you can actually customise your army for fighting against them.

If they’ve become stronger then you need to be opportunistic. Look for when they get into other wars, preferably ones that would take them a while to win and go after them. Watch where you’re taking battles, try to get them in good terrain. Keep a good reserve of money for hiring mercs.

There's a whole lot of context questions you need to ask. Have you done any military research? What's your generals like? Is your army maintenance set correctly?

Tremendous amount of capital in the bank and just merc spam them.

You deserve it for playing the antagonist. Rome is the objective protagonist of history thus they are destined to win.

Furthermore, Carthago delenda est.

I've even seen AI Etruria beat Rome, so ig you're worse than the ai 😂