In our group, we depict Leadership as a combination of mental stats, skills, level and roleplaying. Do not underestimate the importance of Knowledge (fill in area of expertise) for a good leader. The PHB suggest (history) as the means to represent the knowledge of war.
That said, I don't think that a pure Fighter is a good choice to represent a good leader. (Nor anything else, for that matter.
)
If you have the Mini Handbook, toss in some levels of Marshall. The Aura's do a nice enough job of representing leadership on a battlefield.
Personally, I think the Book of Nine Swords (Tome of Battle) has the best way to represent leadership via the White Raven Discipline. The book adds a ton of options to melee combat, which makes it intresting, and it isn't overpowered at all. (Remember, wizard 20 is pure core.
) I wholeheartidly recommend this book to you.
If you really, really want to stick to Fighter, grab some Marshall levels, some Bard levels (roleplay this as the ability to rally your troops via Perform (oratory), to avoid the classical image of a bard) and spend skill points on Knowledges...
Edit: This combines the Marshal with Tome of Battle:
Sublime Way variant Marshal - Wizards Community