I'm sure you're probably familiar with the concept of dèjà vu, the existential feeling that you've seen or done something before. Well, playing Rome: Barbarian Invasion isn't quite like that. It's more like the sensation of presque vu: the feeling of almost remembering something you may have done or seen before. Barbarian Invasion is strongly and identifiably Rome: Total War, but there are some subtle differences to the game mechanics that just alter the experience of playing the game enough to prevent you from thinking that you've seen all this before.

Like the previous expansions to the other Total War titles, Barbarian Invasion moves the epoch beyond that of its parent game, adds scores of new units and tightens the main campaign into far sharper focus. Here, the scale of the campaign map has not been diminished from Rome: Total War, but the victory conditions aren't quite so all encompassing. Indeed, the ten different playable factions have individual criteria that they must fulfil to achieve a campaign victory; the two halves of the Roman Empire are given the toughest tasks, needing to achieve control of 34 settlements on the campaign map; factions such as the Huns, however, have an easier time and will only need to assume governance of 15 regions to achieve victory, for example. The difficulty of each faction's campaign is determined not just by the number of settlements they need to control for victory, but also which particular strategic regions are of particular importance for your faction and must be controlled before the game can end. The Roman factions, obviously, must end the game with Rome itself under their control, whilst a race like the Sassanids will place a far greater importance on the control of Palestine.

You are free to pick any of the ten available factions to play, without being compelled to play through as the Romans first. Given that the Roman Empire is historically in decline at this point in time, this explains the higher difficulty level of the Roman campaigns, so you're positively encouraged to play using the other factions first. Should you choose to play as one of the smaller factions, such as the Goths or Franks, early expansion is key; if you take too much time to consolidate your fledging empire before you start picking fights with your neighbours, you're going to get a very nasty surprise after a few turns. With the Vandals fleeing west, hotly pursued by their tormentors, the infamous Huns, having your capital city engulfed by several thousand hostile Vandal warriors is going to give you a very large, and very possibly fatal, headache.

You can, of course, eliminate (or at least minimise) this threat by playing as either the Huns or the Vandals, and this allows you to experiment with one of the more interesting game mechanic tweaks. Certain factions will form a horde if they lose all their settlements. Playing as a horde has its advantages and disadvantages. The most obvious advantage is that you don't have to pay maintenance for your military units. Mercenary units must still be paid in full each turn, but if you spend your time as a horde wisely and sack enough settlements, this shouldn't pose too much of a problem. The disadvantage of playing as a horde is that your strength is gradually diminished engagement after engagement, and the financial viability of using mercenaries to compensate for lost units rapidly becomes unrealistic. It eventually becomes imperative to finally settle down, both from a financial and military point of view. Finding the right time to actually do so will probably be the key point of your campaign. The Huns in particular have such an overwhelming advantage in the potency of their cavalry that settling too early will rob you of the opportunity to run riot over the majority of Northern Europe and deal your enemies a fatal blow.

Other advances to the game model include the influence of religion on the population of your settlements. Paganism, Christianity and Zoroastrianism (an early precursor to Islam in Persia, and the dominant faith of the Sassanids) are all featured. Religion complicates the management of settlements. Serious order problems can be caused if the city governor does not share the dominant faith of its populace, especially if your garrison isn't large enough. Religious conversion can be carried out, but is quite a slow process and doesn't make a huge difference as to how you play the game. The one significant change to the tactical aspect of the game is the addition of the ability to fight battles at night.

Night battles are stupendously impressive spectacles, especially if you have a couple of units of archers. Watching flights of fire arrows arc gracefully through the sky in the darkness is wonderfully atmospheric. Night battles occur only when they're forced upon you, or if one of your generals is sufficiently skilled to conduct nocturnal engagements. Army captains can never initiate night battles, so it is to your tactical advantage to use the night fighting ability of your generals to fight after dark if the opposing army is commanded by a captain, or an opposing general without the trait. You will need to use every conceivable advantage you can muster, too, because the AI is as impressive as ever. Barbarian infantry units can make use of two new special abilities: the shield wall and the schiltrom. The schiltrom is arguably the more useful of the two, as it is particularly effective against cavalry and prevents your infantry units from being flanked.

It's not like the French to make a capitulating retreat, is it?

So then, the tactical play is as brilliant as its parent game, and a plethora of new units have been added, plus the fantastic spectacle of night battles. Religion and the horde mechanic both make their presence felt on the strategic aspect of the game, but that nagging feeling of presque vu remains. With the miserly addition of just two new Historical battles, no graphical improvements to the 3D engine at all (other than the night fighting) and a barely changed campaign mode, Barbarian Invasion doesn't quite do enough new. Not that I'm trying to suggest that the game exhibits the same level of decline from its predecessor as the post-363 AD Roman Empire, far from it. Barbarian Invasion is still at its heart Rome: Total War, with all that implies. In terms of historical authenticity and realism of the battles, the game is still peerless.

Flaws from Rome remain, however: namely, the realism-jarring Australasian voice cast. I'm not sure exactly what kind of accent a 4th Century Goth actually had, but I'm certain that you couldn't place it in downtown Sydney. There are some new musical cues, but the majority of the score is reused from the parent game, which is a slight disappointment. The expansion pack is also aimed more at the player who will commit a lot of time to the game - i.e. long-term players of the original - so the difficulty level of the campaign may put off less experienced players. Had the game not stood still graphically, and had there been a few more improvements to the tactical and strategic halves of the game, this could have garnered a score to match that of its predecessor. As it is, Barbarian Invasion is still probably one of the finest strategy games you'll play this year, but will probably leave you with the feeling that a little more could have been done to justify the entry fee.