As awesome as trebs are, they still die when thrown against a city. With CR2 maybe one out of three survives against longbows (either killing or withdrawing, and usually not the first one), but the basic assumption is that they die while dealing collateral damage. Suicide cats don't survive - they just die.. I'm used to giving them CR2 out of the barracks (or rather just before using them) assuming I build them under warbuild civics (vassalage and/or theocracy), but have just started thinking about it again - why CR and not barrage? Obviously with CR promotions they have higher survival rate, but that's not really their job, collateral damage is, so maybe Barrage 2 would be better? Then again, CR3 trebs actually have a decent chance of surviving, so they lucky ones that get there might actually stay alive to get fourth promotion. Of course I like having three accuracy trebs in the stack as well to take out cultural defenses before going for the kill, but they don't attack anything - they just bombard. Therefore they don't gain xp and thus no promotions over accuracy either, which doesn't matter because that's all they do - bombard. Also, is Drill of any use for them? Do first strikes matter when they are thrown in to die while softening the defenses?