Though not required to command an army, a capable general can increase the potency of your soldiers. Any named character can become a general but its wise to be selective and choose a named character with some "stars" under the command statistic that you can build upon.
As you continue through the Imperial Campaign, new named characters will be added to your roster. When youre notified of an impending wedding, scan over your daughters suitor and gauge his potential as a future general before giving your blessing. Deny your daughter if her possible husband isnt up to your standards and rate another potential named character some turns later.
Note that named characters also gain an entourage. These characters provide bonuses to your named characters and can actually be exchanged between named characters. You may want to convert a general into a governor and add some management bonuses or perhaps the named character is about to perish--he takes his entourage with him so its wise to trade off those bonuses before you lose them.
Like a governor gaining management skills through prolonged management, a general builds his command statistic through successful battles. Therefore its important to keep your general intact through each battle so you build his command statistic and improve his ability to influence your troops. A general does this by strengthening the skill and morale of the troops during the battle; your soldiers fighting near the general receive the biggest boost.
Obviously its wise to keep your general as safe as possible, though your general and his bodyguards are more than capable fighters. Dont use your general unit against counter forces. If possible gain the largest advantage possible when sending your general unit into battle; for instance, use a flanking maneuver to hit an enemys rear side or battle enemy forces already engaged with other ally units.
A generals death is like toppling dominos. It affects the morale of your troops and will cause your forces to rout much faster than if your general was present and healthy. Likewise, eliminating an enemy general can turn a battles tide in your favor or just quicken the inevitable. This is why taking care of your general is important. You might be winning the battle then all of a sudden you carelessly lose your general, causing your troops to panic. If you do survive the battle, you may incur many more losses than you would have otherwise. Plus if your general dies in battle, he cant reproduce and continue that family line.
Fighting the Smart Fight
Its important to remember that Rome: Total War battles arent simply about numbers. Obviously its to your advantage to have more troops than the enemy you attack but if you dont fight the smart fight, those numbers can dwindle very quickly. Conversely, you could be far outnumbered by a computer-controlled enemy and still emerge victorious if you fight the smart fight and use counter unit situations properly.
There are some generalities you can make about unit types, though its best to read each description to discover their true strengths and weaknesses. But in general, archers are best used against slower moving infantry; cavalry are best used against weakly armored ranged units; and infantry are best used against cavalry units. Specifically, though, its spearmen that counter cavalry; infantry can hold its own against cavalry but spearmen are true counters. Heavy cavalry are generally best used against lighter cavalry.
Protect your ranged units against a cavalry rush by keeping infantry and spearmen units close. Cavalry can decimate an archer line with very little effort. On offense you should look for an opportunity to rush ranged units with your cavalry groups. Avoid remaining within range of enemy archers unless youre setting up an attack. On the flip side, inflict as much damage from a distance as possible. Weaken your enemys infantry or cavalry units from long-range with your own ranged attack.
Elephants are fierce adversaries. Units like war dogs and incendiary pigs can help counter elephants; both of these smaller animals frighten the elephants and can cause the large animal to run amok and even crush its own ally forces. Spearmen, the counter to cavalry, also work against elephants (preferably surrounding the beast) and even skirmishers can prove effective. In skirmish mode, ranged units can attack and retreat to keep ahead of the enemy elephant.
Use unit groupings to help keep track of counter groups. For instance, place your general and his bodyguard in one group, so you can recall the squad quickly and maneuver them toward your fighting soldiers to help boost morale (or to even engage the enemy). Place cavalry in another group to set up a flanking maneuver. Set your ranged units in another group to easily switch targets or recall them to retreat from charging attackers.
Avoid battling counters. Dont charge cavalry at a group of spearmen or leave archers alone against approaching cavalry. Also watch how the enemy sets up its forces. If enemy reinforcements begin behind you, dont sit still and wait to be surrounded. Move from the middle or mount a faster attack against one group to avoid fighting both.