The Roman Empire was one of the mightiest empires Europe has ever known. They held complete dominance over the Mediterranean and would last for hundreds of years, finally falling in 1453. In Hearts of Iron 4, players can take control of Italy and restore the Roman Empire by conquering its historical borders.
As Italy, keeping up with your surrounding countries in military buildup will be very difficult. Having a tank-based army is practically impossible, so armies will be built around infantry and artillery, as well as the superior firepower doctrine. While many players usually avoid trade if they can, I prefer never to run a shortage and instead trade as soon as I am notified of one.
Overall, for national focus I will focus on improving my industrial capacity and getting war justifications, although you can mostly do what you prefer with them.
This game was played on Ironman mode with historical focuses on. In addition to that, all available DLCs as of version 1.10.7 were used.
Situation in 1936
As far as setup goes, be sure to begin building civilian factories on the peninsula, switching to military factories after you make five. Always keep industrial and engineering research up to date while also snagging new infantry weapon technologies when they unlock. Ignore aviation technology besides new fighters while prioritizing new cruisers and destroyers for naval technology. That covers the setup portion. Now, let’s take a look at the map.
Italy is one of the few countries that begins the game at war, which can be an incredible advantage. Experience gained from battles can be a potent tool to modify unit templates and create a stronger army. The war in Ethiopia is relatively easy, leaving the player with two options. You can either rapidly invade and win the war, either annexing or making puppet states of the territory. Alternatively, you can delay the war and extend it to farm more experience.
While at war with Ethiopia, watch your political power rise and justify a war against Austria once you have the political power. We need this territory to reform Rome, and it has the benefit of weakening Germany.
Early European Conquests
Once Ethiopia is defeated, do what you want with them, although I prefer to puppet them. Allocate around two-thirds of your troops back to Italy while using the rest to take defensive positions in Africa. Before your claim on Austria is complete, be sure to draft a battle plan focusing on taking Wien. During the wait, the Spanish Civil War should start, which you can send volunteers to if you are looking for something to do.
The war with Austria should be brief and easy due to their low industrial capacity and manpower. Be sure to encircle what forces you can and prioritize taking the capital immediately. Following the war, expand your military recruitment to include at least ten infantry regiments at a time.
Afterwards, the goal will be a war with Yugoslavia. Unfortunately, this is complicated by them being guaranteed by France and Czechoslovakia. The solution? We are going to quickly rush down our national focus tree to war with France and strike before they can join the allies.
War with France
Continue expanding your military and make plans to invade France. I will have two armies directly invading the French border while also launching a naval invasion from Sardinia. While working through the focus tree for the French war justification be sure to have your affairs in Africa in order so that you don’t lose on that front.
Once you declare war, hold your positions for a few weeks while the French attack you. This will whittle down their limited manpower and give you an advantage once you are pushing. Don’t forget to utilize your airforce, but be careful with your navy. Oil supplies will be too low for your navy so use them sparingly. I would advise only using your navy to launch the naval invasion before sending them back to port.
Launch your battleplans into France once they have lost around 100 thousand soldiers. It will be slow at first, but once you breakthrough, it will be smooth sailing. They have several modifiers that reduce their stability and their ability to fight, making the war a relatively simple matter.
After the fall of Paris, the French capitulation will shortly follow. The exact details of the peace deal are up to the player, but be sure to take their territory in Europe, North Africa, and Syria for yourself. You could annex all of the formerly French territories, but I puppeted most of them including making France a puppet state on a few random islands. This preserves the French Navy so that they will aid you in your future fight against the United Kingdom.
War with the United Kingdom
At this point, there aren’t many challenges to your dominance in the world. With the industrial capacity of your conquered territories and the manpower from your puppets around the world, Italy is in a very strong position.
Begin focusing on internal development, building military factories and oil refineries to fuel the war machine. By 1939, you should have a significant land military and enough industry to support it. In order to declare war you will need a war justification which you can get from your national focus tree. Relocate your navies to the English Channel and prepare multiple naval invasions. Alternatively, you can use air superiority and paratroops to land them on the island. With the assistance of the French Navy and your other puppets you should have no problem achieving naval superiority.
Immediately prioritize taking harbors once you land to supply your forces, then proceed to take victory points. The British have bonuses to stability which will make them tough to capitulate, but it is easily done once you have a foothold on the islands. Once again after the war take control of their European land and any possessions in the Middle East, but leave them something for you to puppet. At this point you will have control of the three of the most powerful navies in the world.
Forming the Empire
Every major country you need to form Rome has been defeated; all that remain are minor countries with nobody to protect them. It will be a relatively simple matter to conquer them and restore the empire.
Here is the list of countries that need to be annexed for you to form the Roman Empire, which can also be found in-game under the decision. In addition to these be sure to hold all of North Africa, Gibraltar, and Malta.
After this series of easy conquests, you will have the decision to form the Roman Empire. Congratulations, you have accomplished feats unheard of since the times of emperor Trajan in 117 AD.