Dynasty Warriors as a series hasn't changed much over the years. Sure it's had its playable character roster expanded significantly, and it's had the odd combat system overhaul here and there, but the core concept has always remained the same: it's one super overpowered Chinese warrior (you) versus entire armies that flood the screen. To be fair, it's a formula that's given Dynasty Warriors a unique identity – a formula that fans have come to love and a formula that, for the most part, works well.

In a lot of ways, Dynasty Warriors 9 feels like a reboot. It's easily the most altered mainline entry in the series' history, thrusting the hack and slash action into an open world setting. It's ultimately a risk. Why fix what isn't broken? Is it to try and attract a new audience? Or is it an attempt to simply refresh a series that's often been criticised for growing stale and repetitive? In truth it's probably a bit of both, and the resulting game is the most ambitious Dynasty Warriors title to date – but also one of the most disappointing.

By going open world, Dynasty Warriors 9 abandons much of the series' established structure. Instead of choosing a story mode or a stage before jumping into the chaos with your favourite character, you're now diving head-first into a gigantic map of ancient China, seeking out the next critical mission that moves the story along. The new formula takes time to click. At first, we really struggled to understand what good an open world is to a game that's all about getting lost in over-the-top battles, but it does start to make sense as you delve deeper into the experience.

Unfortunately, the release doesn't make a great initial impression, whether you're a fan of the series or not. The opening story chapters of the game are dull and monotonous, with little more than small skirmishes dotted about the map. It's not until later on that it truly feels like you're part of a vast army going up against an equally impressive legion of enemies. It's here that the open world starts to make sense, allowing for some colossal clashes across huge swathes of Chinese countryside. Dynasty Warriors has never felt so organic.

It's this same open world that also contributes to many of the game's failings, however. When it's not covered in thousands upon thousands of soldiers, the map's shockingly barren – even cities and towns feel lifeless when they're supposed to be bustling hubs of culture and trade. There are side activities that you can try your hand at – fishing, hunting, material collecting – but none of them are entertaining or even worthwhile. And of course there's an unnecessarily convoluted crafting system in place, demanding that you gather laundry lists of items so that you can create weapons and accessories – equipment that's quickly made redundant by the nearest shopkeeper's stock.

With nothing else going on, you'll find yourself just travelling from one mission to the next, capturing the same bases over and over again as you go. While it is satisfying to carve out a path for your army to follow, there's no denying that proceedings start to drag when an objective is way off in the distance. Fast travel is an option, taking you straight to the nearest mission starting point, but without a road that's free of enemies, you'll usually find that your allies frequently stop their march to deal with even the lowliest foe. If you're not prepared to take it slow, things can get tedious very quickly.

The new open world structure also impacts how the classic Three Kingdoms story is told. In essence, each big historical battle has been stretched out over individual story chapters, with dialogue and cutscenes occurring at set points. Each of the warring kingdoms has its own storyline, but you follow the plot as your chosen character, meaning that, at times, you'll see things from their perspective. Strangely enough, this allows Dynasty Warriors 9 to explore events in greater detail. Without the need to quickly jump from one scenario to the next, it's free to illustrate the finer points of each conflict, and we're sure more dedicated fans will appreciate that.

Some characters get a lot more time in the spotlight than others, though. No matter how well you perform within the story, proceedings don't deviate from history, so it's possible that your chosen character will be killed off just a couple of chapters in. The warlord Cao Cao, for example, lives through six or seven acts before he finally snuffs it, while stoic warrior Pang De only hangs around for two before he's taken out. The thing is, unless you know your Chinese history, you might end up selecting a character who only gets you through a small chunk of the story – and that can be a bit frustrating when you're just trying to unlock later chapters.

Meanwhile, much like the open world, the overhauled combat system also has its ups and downs. Mashing square gives you access to 'flow' combos, which are basically your bread and butter attacks. On top of them, you've got specific techniques shared by each and every character: a launching move, which knocks your opponent into the air; a stunning attack, which opens your foe up to further damage; and a knockdown blow, which forces your enemy to the ground for a few seconds.

They may be three different techniques, but these moves all serve the same purpose in that you'll use them to extend your combos. Couple them with the new lock-on mechanic, which allows you to – gasp – actually lock on to key opponents, and you've got a more combo-focused system. It's fun enough, but it feels like a lot of individuality has been removed from the character roster as a result. Everyone has the same basic suite of attacks barring a unique special move that can only be used once every 30 seconds or so.

This issue is amplified by the fact that many characters have had their signature weapons taken away. Where Dynasty Warriors 8 ensured that every officer got their own unique moveset, Dynasty Warriors 9 brings back the clones, with some characters sharing weapon types and fighting styles. It's a real shame, because the varied movesets of games past really helped each hero stand out, and gave you more reason to take them for a spin.

Whether it was budget or time that stopped Omega Force from fully fleshing out the playable cast, the unfortunate truth is that Dynasty Warriors 9 feels rushed across the board. Despite being in development for at least a few years, the game's bogged down by bugs and graphical glitches. The open world doesn't have any load screens, but noticeable pop-in is a regular annoyance, with whole squads of soldiers just blinking into existence at times. The kicker is that aside from some nice lighting and weather effects, the title looks seriously dated.

Worst of all, however, is that the game struggles to maintain a consistent framerate – even on PS4 Pro. There are two graphical settings to choose from: one prioritises resolution at 30 frames-per-second, while the other opts for a “stable” framerate. The reality is that neither works very well. The former tanks the framerate to unforgivable levels during bigger battles, while the latter gives you that “stable” framerate, which seems to jump between 10fps and 60fps depending on how much action there is on screen. It's just not good enough.

Speaking of not good enough, the English dub is abysmal. Dynasty Warriors is well known for its sometimes hilariously camp English voice acting, but recent instalments have featured decent work. Sadly, this isn't the case with Dynasty Warriors 9, which has thrown all the old voices out the window. Now, it sounds like over 100 characters have been voiced by three different people. Many of the new voices barely fit the characters that they're assigned to, and the delivery is often painful. It's so bad that it goes beyond being a joke and simply cheapens the entire experience. Thankfully, Japanese and even Chinese dubs are included.

Conclusion

Dynasty Warriors has been on a steady run since it fumbled with the divisive Dynasty Warriors 6, and now it's in danger of fumbling all over again. Dynasty Warriors 9 goes open world and the result is a game of extreme ups and downs. For every gloriously huge battle there's a boring stint of traversal across a dreadfully barren map. For every interesting story moment or interaction, there's a horribly ugly graphical glitch. Factor in an unconvincing combat system overhaul, and you've got a Dynasty Warriors title that may disappoint even the most dedicated of fans. There's still some good historical hack and slash fun to be had here, but we expected much more from the return of this flagship series.