HOI4 Dev Diary - News from the Eastern Front
podcat, Oberkommando HOI4
Hi everyone! It’s time to touch base and start talking about what we have been up to since we released 1.6.2. We have been both preparing to start on the next big expansion which will come together with the 1.8 “Husky” Update as well as working on various tasks for 1.7 ‘Hydra’ which is the next upcoming release. Let's jump in. Beware, it’s going to be pretty wordy!
HoI4 Dev Diary - LaR UK AAR
YaBoy_Bobby, Game Designer - HoI4
Join me as I recount some of the highlights from my recent prerelease testing playthrough of LaR in this After Action Report (AAR) where played I as the UK.
Phase 1: The buildup
So first up, why 1.7? This is because we are now going 64-bit which will mean you can no longer run HOI4 on 32-bit, so we want to make it clear it is a different technical base. More on this next dev diary though.
We have also worked on some of the bugs that have popped up since then, most importantly front issues for Germany vs Soviets. This was something that was reported during 1.6.2 development, but as we dug into things it turned out to require a lot more work than we had planned. We made the decision to do it for 1.7, and instead of just fixing that particular issue we also reworked a bit of how fronts and the ai work. This is going to be what the diary will be about today!
When playing the UK in singleplayer I don’t really like trying to hold France, as I feel doing so kinda ruins the pacing of a historical playthrough. So I spent all my time from game start only building civilian factories with about 85% of my mills making aircraft. I also began establishing my intel agency in late 1937. I focused on improving my intel generation and code-cracking ability first so I could give some force multiplication to my rather small army.
Phase 2: Naval Dominance and Focused Defense
At the start of hostilities, I began cracking Germany’s encryption and used my airforce in the Mediterranean in conjunction with a large part of my navy. I figured it wasn’t worth sacrificing too much air strength against Germany in France at this point. I had just switched to building military factories from only building civilian factories, so I could not afford to use my more limited airforce recklessly. I also set up the majority of my operatives to set up intel networks in Germany.
Oh and because people will ask... we are not super far away from the 1.7 release. We plan to let you help test it in open beta soon (where soon means like “within a week” or thereabouts).
I attempted to recruit mostly “seducer” trait operatives as they have a lower chance of being caught. In the process, I got some interesting seduction experts.
What’s new on the eastern front?
Operation Barbarossa, which is the German invasion of the Soviet Union, is one of the pivotal balance points in HOI4 (and in all the HOI games) together with the fall of the low countries, Poland and the Sino-Japanese war. After 1.6.2 we had Germany beating the Soviets a bit too easily, and in particular, players had too easy of a time doing it. This had a lot of different reasons. The primary one is that we spent a lot of time overhauling the German strategic and planning AI which has made it very consistent and strong. Additionally for the AI, being good at defending is a much harder job than being good at attacking. What wasn’t working properly was that when the Soviets finally fell, it was often due to an issue related to frontline stability. The Soviet AI would misprioritize this and move a large part of its front elsewhere, leaving a hole that the German AI would often exploit (which players also definitely did). It’s also not fun beating an AI when it makes such a critical mistake. This particular case was extremely random, but the front reaching Crimea was a common factor. At that point, a new front would open at the same time as the line became long enough to require multiple Army Groups to cover it, which was another weakness for the AI. A lot of those technical issues should now behave a lot better and we are consistently seeing much better performance from the Soviets. Although, they do still generally lose in the end, but this is mostly by design.
To explain why this is a good target, let’s look at our balance targets for Barbarossa:
The Axis pushes the Soviet line in slowly until the Soviets lose in 1945 unless the Allies secure a big landing and relieve the Soviets, at which point Germany should start losing with its forces split across the 2-3 fronts.
So why is this a good target?
Most of my rather small army was deployed in Egypt to hold the Suez. With air superiority and an intel advantage over the Italians, Holding Egypt was a great success. I was able to recruit the famous Nancy Wake and I decided to send her on a Roman holiday to help me get more intel on Italy since I would be fighting them in Africa for the foreseeable future.
Phase 3: Battle of Malta
As an Axis player, it means business as usual. You get to beat the Soviets, and the better we make the German AI (which does the heavy lifting), the more challenging we can make it for a player Germany and still retain the balance target.
As a Comintern player it means you need to defend, hold out, and push back Germany. Here, the stronger we can make the German AI, the more challenging it is for a Soviet player. So to keep our balance target we want to make the Soviet as tough as possible, but on their own, they need to break by ‘45.
After the Italian navy was largely defeated, I infiltrated the Italian airforce to help get a more clear idea of how close I was to breaking it. At this point, the Italian airforce started port striking my Mediterranean Fleet in Malta. After looking at their plane counts in the intel ledger, I built up some radar in Malta and deployed the airforce to intercept the Italians in the region. Baiting them to bomb my exposed, and no longer as useful, fleet worked as phase one of my plan to break the axis airforce.
As an Allied player, you have a bit of a race on your hands. A Germany that has beaten the Soviets will be a very difficult target, so you need to build up your strength and preferably strike when the German army is as extended, as it will get some solid landing points (ai is better at defending too now, so this is not always so easy). From abalance point, we need to make sure that the eastern front holds up long enough for you to get ready to do this. If the Soviets can push back the Germans on their own, there is no reason to play someone on the Allied side. If Germany beats the Soviet too fast, you will not have time to get involved (especially since the Allies are much more spread across the world and contains more minor nations we wanna make sure can make it to the party).
Hopefully, that clarifies how we think about stuff. At the moment the allies do ok in Africa, but pulling off consistent D-Day scale invasions is something we have as more of a long term goal we are working on. Invasion skill for the AI has improved a lot, but the AI has also gotten better at defending. We have thought out a long term plan to also tackle this, but it requires a lot more strategic planning on the side of the AI with respect to theaters, so it is something you will need to look forward to in the future.
Meanwhile, In Germany and occupied France, my intel networks had become rather strong and were providing good info on the state of the axis. I had at this point also infiltrated the German civilian govt’ and army to open up further options for operations and to get a more clear picture of their strengths.
By late 1940 I had broken both the German and Italian ciphers and had weakened both the German and Italian airforces by fighting in favorable conditions where I had a large radar advantage combined with my passive cracked crypto advantage. Having enemy ciphers broken increases interception efficiency as well as adds to air detection.
Phase 4: Battleof Greece
AI in Hearts of Iron is a very complex problem and something we will always be working on improving. It will never really be “done”. We are feeling a lot better about the eastern front now and shuffling issues there, but there is, of course, lots of work left to do everywhere. It won’t fix everything, but I hope it will feel a lot better when you get to try fighting the Soviets again in 1.7.
At the end of 1940, Greece was invaded by Italy and Germany. By this point, I had a significant intel advantage, was close to matching axis airpower, and had a large and equipped Free French volunteer force. I decided I would turtle southern Greece as long as I could and brutalize the axis in the air in the process. I scrambled a large part of my North African forces to Greece and deployed the majority of my airpower. At one point my defensive line was nearly broken. I was able to save it by activating my broken ciphers on Germany, giving myself a temporary 30day combat. Before the buff expired I was able to get some extra forces in and save Greece.
So while I am talking about AI, let's take a look at some of the tools we use to stay on top of the strategic situation and to help find relevant savegames, etc.
Every night we run several machines hands-off that record various data for us and lets us chec kwhether we broke something, measure improvements, etc. Loading 30 savegames every morning and going over them is neither fun nor effective, so we have developed this awesome web tool that gives us a quick timeline and map to scan over:
Heat maps also make it easy to scan over time and see where the AI is distributing and focusing its units. This example below is highlighting the Japanese forces late 41:
By mid-1941 I had overtaken the axis in the air and southern Greece looked more and more secure. I decided it was time to start boosting resistance in France and laying the groundwork for eventual liberation. I also was well on my way to cracking the new Italian and German ciphers.
Unit Controller for Players
So that was
Once the ciphers were cracked again and my tac bombers were no longer needed in Greece, I decided to start harassing the Germans with a strategic bombing campaign in their homeland. With my Intel levels, I was able to track how my bombing campaign was impacting Germany. I had also begun targetting resource-rich areas in France with targeted sabotage operations to further put stress on the German war machine.
Phase 5: Yugoslavian Uprising
Over the course of the next year, America and Vichy joined the war and a fight for North Africa broke out again. With Intel and Air advantage pushing Vichy France back was pretty easy. During the North Africa campaign, I noticed that Croatia was barely keeping occupied Yugoslavia under control. So I sent some of my Operatives to support the resistance there, pushing it over the edge and causing a full-scale uprising. Many of the Axis forces in northern Greece were then cut off and annihilated.