When it launched on the Sega Mega Drive / Genesis back in the very early days of the system, Techno Soft's Herzog Zwei confounded quite a few people. It came from a studio which – in the west, at least – was most famous for its Thunder Force series of blasters. The top-down perspective looked similar to the free-roaming overhead stages in stablemate Thunder Force II, which led many to assume it was the same kind of deal. In reality, Herzog Zwei – so named because it's the sequel to the MSX and PC-8801 game Herzog, which means "Duke" in German – is a totally different kettle of fish; in fact, it's credited as being instrumental in the evolution of the Real-Time Strategy genre and is cited as an influence by the developers of RTS titles such as Dune II and Warcraft.

Still, it's easy to see why that wasn't immediately obvious back in the early '90s. Rather than controlling a mouse pointer – as you might expect in other RTS games – you're actually placed in the cockpit of a fighter jet which is capable of transforming into a robot at the touch of a button. In both modes, you can call upon a fairly powerful projectile attack which is used to dispatch enemy units and the opposing commander, who also zips around the 8 available arena-like maps in his own morphing mech. Your craft has an energy gauge and fuel gauge; the former is depleted when you're attacked and the latter is consumed by movement. Either of them reaching zero causes you to dramatically explode and respawn back at your HQ, which is located in one of the corners of the map, but you can restore both gauges by hovering over said HQ or any friendly outpost. You also have an ammo gauge, which, once depleted, leaves you unable to defend yourself.

Your objective – which is shared by the enemy commander – is to attack the opposition HQ until its energy level is reduced to zero. The catch here is that your robot's cannon is incapable of damaging your rival's base, and you must instead rely on your army of foot soldiers, attack cycles, tanks and boats to get the job done. These units have to be manufactured using money which slowly builds up during play; the more outposts you control on the map, the faster the cash flows in. Outposts are 'taken' by sending in four of your foot soldiers, and it's possible to steal them from the enemy, too. Because there are always 9 outposts on each map, there's rarely a stalemate situation where both sides have the same amount of bases, which keeps things lively.

At the point of constructing a unit, you have to select what command you want to give it. These range from the basic "patrol this area" order to the vital "attack the enemy HQ" command, and understanding which one to use in any given situation is a massive part of success in Herzog Zwei. For example, it's no good giving a tank a "patrol" command if you want it to remain next to a vital outpost and defend it. Units also have their ammo, fuel and energy gauges, and these can be restored if you pick one up and ferry it to a friendly base. Alternatively, supply trucks can restock other units with fuel and ammo (but not shield energy), with the caveat being that these particular units have no means of defending themselves, so they must be protected if you want them to be effective in the field.

Once a unit has been constructed, you can pick it up from any of your outposts in your jet fighter mode and airlift it to the position you want on the map – assuming, of course, you don't get taken out by the enemy commander or one of his anti-air missile units, or run out of juice en route (fuel is consumed at a faster rate when you're carrying a unit). Units that are in trouble can be picked up in this fashion, too, which gives the game a gloriously hectic feel; even when the tide of battle is very much in your favour, there's always something to do somewhere on the map – be it defending your base from hostiles, rescuing units which have fallen into ravines or simply dealing with the enemy commander, who will be occupied by very much the same concerns as you are. In particular, the contest to hold onto the 9 outposts is something you'll spend a lot of time on; because you lack enough fuel to simply ferry your forces directly to the enemy HQ, controlling these bases is essential as they serve as staging posts for your conquest.

Herzog Zwei is a dense and complex game, then, but you could never accuse it of lacking balance. Every unit in the game can be dealt with effectively once you understand how things work. The anti-air units are capable of picking the opposition player's fighter jet out of the sky with a few well-timed, heat-seeking missiles, but they can't defend themselves from other ground units and are therefore easy fodder for tanks. Gun emplacements pack the most deadly firepower and can deal with both ground and air units, but they're totally static – motorbikes, on the other hand, lack the grunt to contend with heavy armour but they're incredibly fast and therefore ideal for scouting or drawing out enemy units into traps you've set elsewhere on the map. Furthermore, each unit has a different cost and build time attributed to it, so the weaker units usually cost less and take less time to make than the stronger ones. Learning how to mix and match your forces is key; missile launchers need to be defended by tanks while weaker foot soldiers – the only ones capable of occupying outposts, lest we forget – should be escorted by stronger units whenever possible.

What makes the whole experience even more gripping is that, unlike the popular RTS titles which followed it, Herzog Zwei places you directly in the heat of the action. You're not some omnipresent field marshall watching over the action from the relative safety of your base, as is the case in games like Command & Conquer – you're deep in the action yourself, switching from jet to robot form as you ferry troops and deal with incoming enemies first-hand. Finding that the enemy's staunch defences are too robust for your troops? Then why not drop right into the middle of his formation in robot form and take out those pesky units yourself, thereby opening up a gap for your tanks to come rolling in? This makes the game totally unique in this particular genre, because it not only tests your micro-management and tactical skills but also your reaction time and trigger finger.

Furthermore, the 8 maps included offer a wide range of challenges which helps keep the game fresh. For example, Vulkan is set on a planet covered in molten lava which damages your units if they happen to move onto it. Alternatively, Abgrund is dotted with canyons which create a confusing maze-like surface, while Strand is covered mostly by water, which means you have to make good use of your attack boats as well as effectively transporting your forces in jet mode. While 8 maps doesn't sound like a lot, they're varied enough to present a good range of tactical possibilities, and each one encourages you to change your strategy in subtle ways. They can also be tackled in single-player on one of four difficulty settings, which gives the game even more longevity. Progress in the original game was handled via a convoluted password system as the cartridge lacked battery back-up, but in this Sega Ages update you can save at any time.

Were Herzog Zwei a solely single-player experience, we'd still give it a high recommendation, but it's the game's two-player mode which really makes it a solid-gold classic. Playing against another human opponent is one of the most rewarding gameplay experiences money can buy, provided both of you are adept enough with the game's mechanics and can endure the rather narrow split-screen window. It's not uncommon for two-player battles to go on for over an hour as the balance of power swings one way and then back again; it might sound like hyperbole, but this really is one of the finest two-player games ever made – which is remarkable when you consider it's over 30 years old.

This new Switch release takes this appeal to the next level by offering online multiplayer, which means you'll never be short of an opponent. You can choose to either join a random game or create a room, which other players can identity via a four-digit code. Performance is pretty stable on the whole, but we did notice the odd stutter during gameplay. There's also no way of logging a player's skill level so matchmaking is absent, which means that total newcomers could find themselves lumped in with tactical experts who quickly obliterate them. If you like your multiplayer a little more up close and personal, then it's worth noting that Herzog Zwei lacks local wireless play across two systems, which means you'll always have to play on a single machine – and, as is the case with online play as well, the split-screen view is the only option on the table, which means your rival can see your view of the action at all times. It would have been nice to have the full-screen view, if only for online play.

This update includes an excellent "Herzog Academy" tutorial mode which does a fantastic job of breaking down the game's systems and mechanics. Set over 12 chapters – each one explained by a wide-eyed female commander who constantly makes humorous references to past Sega titles like Virtua Racing, Out Run, Shinobi and Fantasy Zone – this mode is essential for anyone who has yet to experience Herzog Zwei and even has interactive segments where you're tasked with performing certain objectives to prove you've taken all of the advice on-board. The female commander even pokes fun at the game's obtuse nature and warns against throwing down the controller in a rage when it all becomes too much to handle. It's a nice touch, for sure.

Elsewhere, the usual raft of Sega Ages screen filters is available, while the default wallpaper which surrounds the game's 4:3 screen area is packed with information pertaining to the current status of your bases, units and jet fighter, and even includes a handy mini-map which means you don't have to keep dropping back to the unit construction screen to see what's happening on the wider battlefield. There's also a 'helper' mode which allows you to tinker with various settings to make the game easier or harder; it reminds us of the handicap mode in Street Fighter II. Finally, the game also stores replays of your previous battles, in case you feel like breaking down what went right (or wrong, for that matter).

Finally, special note must be made to the game's fantastic soundtrack, which comes courtesy of Naosuke Arai and Tomomi Otani. Techno Soft has a reputation for creating amazing rock-like game music, and while Thunder Force and Hyper Duel tend to get the lion's share of the acclaim when it comes to music, Herzog Zwei arguably showcases some of the company's best audio work; if you're a fan of MIDI-style '90s game music, then you'll positively adore the soundtrack on offer here.

Conclusion

There aren't many games from 30 years ago that you can truly say have stood the test of time, but Herzog Zwei is such a perfectly-balanced strategy offering that it's genuinely hard to pick fault or suggest how it could be improved or enhanced. Sure, the unit AI can be a little basic, the online play is a bit jerky and the split-screen mode in multiplayer cuts off a lot of your viewing area (and also reduces the ability to launch sneak-attacks) but the core gameplay is utterly fantastic, and remains just as addictive and engaging in 2020 as it was back in 1989, when the game first arrived in Japanese stores. In single-player, the varied map types and scalable difficulty mean that Herzog Zwei will keep you entertained for weeks (if not months and years) but when played with another person – be it locally on the same console or online – this game is elevated to a whole new level of greatness. Even if RTS titles aren't your cup of tea, we highly recommend you give this one a whirl because, outside of spiritual successor AirMech, there really hasn't been a game quite like this since.