As historic context for video games go, World War II is pretty mined out. After the overwhelming glut of WWI-themed shooters and strategy games in the late '90s and early '00s, a deep fatigue slowed the torrent to a trickle.

Yet Paradox Interactive, the developer behind strategy franchises like Europa Universalis and Crusader Kings, bucked the trend with the critically acclaimed (and briskly selling) fourth entry in its Hearts of Iron series.

Renowned for its complex systems and the depth of its combat models, Hearts of Iron tasks players with conducting the war at the highest levels: balancing political and economic demands, creating a massive industrial war machine, and deploying the military might of a global super power with finesse and intelligence. But how did Paradox find a fresh approach to what is easily the most thoroughly documented war in human history?

It begins by incorporating more of the war’s prelude and modeling how technology transformed the battlefield. “A lot of the technologies in HOI4 are things you will only start benefiting from once they are produced en masse--a Panzer IV is no good unless you have enough to make a difference on the frontline,” says design lead Dan Lind.

“We put a lot of effort into making the industrial gameplay and build-up deep and interesting. World War II saw incredible leaps in technology. Nations went from basic equipment to tanks and nuclear weapons in a handful of years.”

Hearts of Iron IV places a lot of emphasis on the industrial nature of the war, and how heavy industry evolved rapidly alongside new technology.

“Technology in Hearts of Iron IV is set up in a way where at the start of the game you have more of a WWI dynamic - units are much stronger on defense than attack and are mostly slower.” The pace of war accelerates quickly, however, as the great powers commit themselves to total war.

“As you acquire technology like fast tanks, doctrines, and air support you are able to maneuver and encircle large groups of enemy troops or more effectively focus a lot of firepower in spots for breakthroughs through blitzkrieg and mobile warfare. In the very late game there are also nukes which are great for breaking heavily entrenched enemies.”

This was never more evident than in one of my playthroughs as the embattled French. With little early support from other tentative regional powers against an aggressive Germany, I had to focus on rapid technological development (and a heavily fortified Maginot Line) and the superiority of early French tanks to survive.

However, because France lacks research boosts that other major powers receive in areas like industry and artillery, I soon found myself ceding territory in a war of attrition against the rapidly advancing German Wehrmacht.

Only a desperate flurry of diplomacy and a carefully executed “bend but don’t break” philosophy allowed me to survive the technological springboard enjoyed by the German infantry and armor and eventually begin to reclaim my pre-war lands, while the Germans were presented with multiple fronts that finally eroded their numerical superiority.

Much of the work of distinguishing Hearts of Iron IV from other WWII games overlaps with distinguishing it from the other Paradox strategy franchises set in vastly different eras, like the medieval Crusader Kings or the space-opera future of Stellaris. Balancing the task of making a standout WWII strategy game with ensuring that Hearts of Iron IV doesn’t end up feeling like a reskin of another game built with similar technology is a challenge.

“We have a shared set of technology called the Clausewitz engine which is used by all projects. HOI4 and Stellaris are on roughly the same engine version,” Lind says. “The biggest differences are the focus on war and the shorter time span. Shorter time span means there are a lot of details that need to be there to provide immersion and make it feel like you are actually involved in the period.”

And that’s another problem that arises when dealing with a relatively recent, compressed period in history, and one that’s so well documented. “Stuff like game balance and AI behavior become vitally important for player immersion to represent events people will be familiar with, and this to a much higher degree than for example supplying events and flavor text and art can deliver. Because it is such a short time period players using hindsight can be a real problem.”

Hearts of Iron IV addresses this issue through systems that require a player to invest in training programs or military engagements before, for instance, restructuring armies or divisions. Just being aware of what the successful strategies employed at the time were isn’t an automatic guarantee of success.

The game also strives to stand out through its presentation of the important personalities that emerged during the war. “Something that sets WW2 apart is that it was one of the last real conflicts where individuals mattered and became personally famous, like Rommel, MacArthur, Patton, and Montgomery. In-game, these people lead your troops, but also gain skill and traits depending on what they’re going through. And they are always present on screen.”

The way these personalities are surfaced is a constant reminder of the human side of a vast, impersonal conflict; they give what could be a flat simulation a sense of character and life that’s lacking in a lot of sandtable or hex-grid style war games.

The conflict itself feels more fluid and dynamic than in many other World War II strategy simulations, as well. Lind attributes this to a focus on a “movement as attack” approach, which means that forces fight their way into a province, rather than both arriving separately and then doing battle in one staged event.

“Instead of large stacks destroying each other, maneuvering is spread over larger areas involving many smaller battles," he says. "This better represents mobile warfare and models advantages with surrounding and attacking from multiple directions.”

Hearts of Iron IV also concentrates on the importance of combined arms and logistics, factors that decided the outcome of countless battles (even the resolution of entire theaters) during World War II. “To successfully win battles, many different type of arms are needed. You need to think about how to support land troops with aircraft and ships.”

It’s a difficult undertaking, attempting to build a game in a period that’s been so crowded and competitive, but one that Paradox approaches with verve and intelligence. 

There’s a reason World War II has gotten so much attention from storytellers and designers and filmmakers: it’s one of the most fascinating periods of human history and one of gaming’s most compelling settings, and it’s heartening to see a fresh take and a considered attempt to pump new life into it.