The word "expandalone" is a hideous, despicable invention - the verbal equivalent of scratching a stick of chalk across a blackboard. If there's a prison for compound-adjectives, "expandalone" deserves to be sent there for the rest of its life. No parole, no visitors.

Unfortunately, "expandalone" does actually do its job when describing Fall of the Samurai. It stands alone from Shogun 2: Total War, and by Jove, it certainly expands upon its progenitor's core ideas. Creative Assembly claims there'll be over 100 hours of play on offer here, and I'm quite prepared to believe them. In fact, it'll probably be more than that in my case; I struggled to win a single battle at this week's showcase. And by "struggled", I mean "failed".

Fall of the Samurai begins in 1869, at the outset of the Boshin War. This is the latest historical period that the Total War series has ever embraced, and as the title implies, it's one that's about to see the Samurai taking a plummet. The British, French and Americans are starting to have a serious influence on the way Japan is being ruled, and this foreign contact has brought several new weapons into play.

The pro-Shogunate and pro-Imperial clans are soon embroiled in bloody civil war - but this time, guns take precedence over swords. There are 40 units in Fall of the Samurai, but the headline new toy is undoubtedly the Gatling gun. You won't get your mitts on these until near the end of the campaign, but they certainly pack a punch when they do turn up. Vulnerable as the crew may be, a well-positioned Gatling will mince any unit foolish enough to approach it head-on.

It feels rather odd to see Doom's iconic chaingun (or at least its Great Grandad) cropping up in a Total War game, a feeling that's only compounded by the revelation that you can manually operate the thing from a new first-person mode. There's no reason to panic: this is just a bonus bit of fun, rather than a misguided attempt to turn the series into a historical FPS. Tapping "H" allows you to assume direct control of certain artillery units, giving you a prime window on the ill-fated Samurai marching into your bullets. In the case of coastal defences, you may also find yourself following the path of a cannonball as you tear into the side of an ill-placed ship.

Naval combat also benefit from the march of progress, to the extent that you'll be able to batter enemy ships with explosive and incendiary shells. More remarkable than that is the fact that certain units can fire torpedoes - this is historically accurate, though I didn't believe it either. These cut through the water with an ominous v-shaped wake, and while they're easy enough to avoid if you're paying attention, they'll do serious damage if they connect. Which isn't surprising, really - it's a frickin' torpedo.

As drastic as all these new additions may seem, Creative Assembly seem to be doing a typically grand job at providing the necessary historical context. One sad little detail sets up an inverse relationship between your technological advancement and the effectiveness of your troops. If you want the really powerful toys you'll need to boost your Modernisation level - but doing this makes your Samurai less useful, and breeds dissatisfaction among your people.

Modernisation is just one entry on a huge list of tweaks and adjustments that should make Fall of the Samurai feel very different to the game that spawned it. Other notable additions include the ability to use your ships to shell land-based units, or to besiege ports. Then there's the aforementioned presence of Western nations, who can become powerful trade allies or provide potent new units. The Foreign Veteran, for example, can plug into an army to boost the experience it gains in battle, or speed up the rate at which a settlement produces units. He can also call out an enemy general for a one-on-one duel; just don't expect him to win any Oscars.

These are fresh ideas, presented with all the attention to detail we've come to expect from Creative Assembly. As much as I hate the term, Fall of the Samurai looks to deserve its "expandalone" title; with this much content on offer, "expansion" feels a bit lightweight.

Fall of the Samurai will be released on PC on March 23.