Another Friday, another diary! Today we will be talking about something a lot of you have been asking about for a long time: The Supply System. This is going to be a big one!

The HOI3 supply system had a lot of problems. It was hard to understand how it worked, and it was hard to know what to do to solve supply problems for the player because it was usually due to missing something some time ago. We even made a separate Arcade Mode for supply which of course nobody used (what self respecting player would pick something called “Arcade Mode”?).

After a couple of glasses of 16yo Lagavulin and some deep thoughts the following problems needed to be solved:

• It must at any point be possible to look at an area and see how many troops can work there without problems. Also for naval invasions.
• It must be possible to see exactly what the bottleneck in your supplies are and give the player possible actions to fix this that are clear.
• The supply system itself must not have long complicated flow networks where cause and effect are hidden by time.
• The supply system must not collapse if a capital is taken which was a big problem in HOI3 and both unrealistic and not fun.
• Holding out in cities should be possible even when cut off from the rest of your force.
• Resistance must be able to hurt your supply lines without being a Whac-A-Mole problem.
• Supply issues need to get gradually worse for a unit rather than feel binary like in HOI3.

Scary list? Sure is, but I think we managed to solve all of it. So how does it work then?

• The world is separated up in Supply Areas, made up of provinces. They are purely for gameplay and generally follow terrain types and such.
• Each area can tell you at a glance exactly how many divisions it can support and how much you are taking up.
• If you hover your mouse over an area it will show you an arrow tracing the path supply takes, and indicate what is limiting it. Areas also have quick buttons for helping solve problems right there (improve naval base level or infrastructure etc).
• The game will show alerts from areas with supply problems to notify player (super useful when you are, say, Britain and spread over many theaters).

The supply level of an area are decided by the following things:

• A local scripted value. Think of it as base infrastructure that can’t really be destroyed (will be basically 0 in mountains and deserts and pretty high in densely populated Europe).
• Any big cities/victory points will increase it. So holding out in these is possible.
• Local resistance movement activity in occupied territory disrupting things for you (we’ll have a separate diary on these guys)
• Incoming supplies from neighbor area. We trace back to capital, or if capital is cut off the next best area. The supply you get is limited by the lowest infrastructure on your route (also possibly sabotaged by resistance), including your own infrastructure level. So for a player what you need to care about is what the bottleneck is, because that is what is going to affect how troops on the front fare. There is also some guaranteed spillover from neighbors to soften the transitions between bad and good areas (simulating that even if decent railway lines stop at a point it’s feasible to transport some distance with trucks or horses etc).
• If we are cut off from home area, say fighting in Africa, or on an island, supply will travel overseas using convoys and be limited by the size of the ports receiving it. So making sure convoys are not sunk and bases are able to sustain you is important before doing any overseas activities.
• Put transport planes on a mission to drop supplies. Useful for cut off troops (this is still WIP so can’t show it yet).
• It also worth noting that supply areas will change size if they are being fought over so actual levels will depend on how much you control.

When a unit finds itself out of supply it has a short period of time where they can live off their own supplies, after that their situation will gradually get worse up to about 30 days when things get very bad. Being out of supply makes you lose organization, move slower, not fight as effectively and take a lot more attrition. Veteran players of HOI know that the best way to beat the enemy is to cut off their supply, encircle them and then destroy them, and this remains true in HOI4.

So how can a player improve their supply situation?
You start by finding the bottleneck.

• Improve infrastructure to allow more supply into the area.
• If linked by sea, make sure to escort convoys and protect them from raiders.
• Build bigger naval bases to allow better throughput.
• Deal with local resistance.
• Research and attach Supply Companies to your division templates to help them manage.
• Airdrop supplies.
• Simply withdraw some troops from an area.

So, what is supply exactly?
In HOI3 supplies was something you produced and stockpiled, then fed into a flow network towards units. In HOI4 the only thing you can stockpile is equipment so this is what you do. Moving, training, fighting, being in bad weather or in particular in bad supply means equipment breaks down and this equipment needs to be shipped. The worse a supply situation is the longer it will take to send equipment and the more attrition you will take. So instead of a flow network we have a system being limited by bottlenecks.

So this means that the abstract “supply” of HOI3 is now instead requests for specific equipment instead which fits a lot better in with HOI4’s equipment and production focus. This also means that there is no separate fuel need as such in the game, this instead is included in production of replacement equipment which need Oil (all tanks, trucks etc). Before everyone chokes on their friday beer give this some thought. Being able to stockpile fuel generally leads to the same problems as all other kinds of stockpiling when it comes to hindsight, so by wrapping it into the actual production of equipment requests to units (also nobody would request a tank without diesel to run it, and if they did it wouldn’t really be usable as a tank) everything clicks into place and player doesn’t have to micro manage all movement, airplane rebasing etc to try to avoid fuel waste and focus on making sure they have access to a strategic Oil resource and replacement equipment and a clear path for units to be supplied.

(p.s dont look too much at the numbers in all these screenshots, we havent really finished balancing supply yet)

Next diary we will take a look at civil wars and coups!

Hello everyone and welcome back to another development diary for Hearts of Iron IV. This week have been rather focused as we are closing in on the beta milestone. Today we’ll take a deep look at USA.

The United States is one of the largest countries in the world in 1936, but the only major power outside eurasia. They control several islands in the pacific, and the Philippines is a puppet. All of the americas is guaranteed by USA at the start as well. Obviously the USA’s states don’t fit 1 to 1 on a game-mechanic-concept, so some lesser states have been merged.

When it comes to resources, the americans live in abundance. They have more than enough of Oil, Steel, Tungsten and Aluminium, and will profit greatly from their exports in the early game. They lack rubber and chromium, but Chromium can be gotten from Cuba and rubber from Brazil, augmented by synthetic production.

USA starts with two national spirits.

• The Great Depression, costing 1 PP every day, until removed in the 1940 election.
• Home of the Free, which allows them to create factions, but not to join any faction led by another ideology.

The US also have disarmed nation & undisturbed isolation as laws from the start, which needs to be changed to unleash their power.

The US Army is not that strong at the start, with 36 divisions, and about half of them being basically garrison brigades.

The Navy is relatively strong, with 3 carriers, 15 battleships, 15 heavy cruisers, 9 light cruisers, 115 destroyers and 77 submarines, but that is just a fraction of the power they will be able to unleash when they have built up.

The airforce is not that big, with less than 900 planes in it, and not yet any B-17’s available .

The focus tree for USA is big and gives plenty of options.

• Issue War Bonds – Allows for powerful bonuses, but only possible if at war with another major.
• WPA & War Propaganda – Targeted buildups depending on which country USA ends at war with.
• Air War Plans Division – What to focus the US Airforce on?
• Bureau of Ships – How to strengthen the US Navy.
• Reaffirm Monroe Doctrine – Turning entire americas into democracies that like the US, with possibilities to create pro-democratic civil wars.

Next week we’ll be explaining why its a bad idea to tell 40 mechanized divisions to attack the Gobi desert.

Well at least it is game related…

Sign up for the closed beta here: http://beta.paradoxplaza.com/signup/48/

Hello everyone and welcome to another entry in the Hearts of Iron development diary series. Today is a bit of chaotic day in the Paradox office, as we leave this office around lunch, and move into the new one in monday morning. I promised a look at France for today,

France is one of the great powers in 1936, one of the winners of the Great War, and in control of a vast global empire. Their heartland in Europe is rich, almost half of Africa is under their control, and they have colonies in Indochina, Syria & Guyana, not to mention direct control of islands in all the oceans of the world.

France has access to all the aluminium and steel they could ever dream of using. They are also controlling some of the biggest supplies of Tungsten and Rubber from their asian colonies. They have no access to oil so they need to import that.

France has three national spirits from the start.

• Victors of WW1, which is a penalty to the speed of land doctrine research by 75%.
• Disjointed Government, which costs 1 political power each day and reduce the national unity until it is removed.
• Protected by the Maginot Line, which slows down planning speed by 25% but increasing their maximum planning bonus by 25%.

France has 74 division in 1936, but several of those are colonial divisions that are only binary, and their armored units are basically brigades. As you can see here on this screenshot, they rely on the heavy fortifications at the border against Germany to defend them there.

France has 1 CV, 3 BB, 7 CA, 7 CL, 52 DD and 57 SS at the start, but it is not a top modern fleet. However, it is strong enough to decisively defeat either the germans or the italians alone, but would have have no chance against a combined axis fleet.

France starts with 456 fighters, 48 Naval Bombers and 204 modern Tactical Bomber. It is a rather good airforce, but it will need to be significantly strengthened before the war starts.

France stands outside of the Allies at the start of 1936, and have plenty of options in their focus tree.

The French Focus Tree has lots of different options.

• The Metropolitan France & Algerie France starting points gives an industrial buildup, and allowes another research slot.
• Defensive OR Agresssive Focus shapes France’s military focus, and the end focus removes the Victors of WW1 penalty.
• Government Reform is a very flexible political tree that can gives France four different options, while eventually removing the Disjointed Government. Start their own faction with Czechoslovakia, join the Allies, join the Comintern or Join the Axis..
• Navy Focus gives research and development bonuses for the navy.
• Air Focus gives research and development bonuses for the air. (not seen in screenshot.)

Next week we’ll talk about Peace Conferences.

Welcome to another development diary about Hearts of Iron IV, this time we’re talking a bit about factions and wargoals.

In different incarnations of the series, factions have worked in slightly different ways, but the common theme have always been there was three of them. Axis, Allies & Comintern. In Hearts of Iron IV that is no longer true. There is no longer any limit on the amount of factions there can be. Germany, Great Britain & the Soviet Union starts off leading their own factions with the usual name you all recognise. The other nations gain the capability to form their own factions through their national focus trees.

So what does a faction do? A faction is a group of nations that can call on each other when fighting a war, and if a nation is overrun while in a faction, they are not eliminated entirely until the faction leader is forced to a peace-conference.

There are of course limits on how to start wars in HoI4. Even if you are a fascist warmongerer you need to have a wargoal to create a war. A wargoal is usually a conquest of a desired state. There are plenty of national focuses that will give countries wargoals if you wish to do some of the more historical conquests. However, sometimes, you may want to do something else, like for example to restore Sweden’s historical borders.

First of all, a democracy can not start a war against a democracy, so you need to switch to become fascist or communist. Democracies are also limited by the fact that they can’t justify against a nation that has not increased the World Tension.

There are a few other faction specific rules for wargoals:

• Annexing or taking non-core territory is much more expensive for Democracies.
• Comintern gets much cheaper wargoals for puppeting people.
• Axis get no cost reduction but are instead allow to declare war without justification if they already have a war ongoing.

Justifying a wargoal usually takes between 6-12 months, and cost a chunk of political power as well. When you have the wargoal, you can start a war against your target country.

Wargoals also has an impact when it comes to Peace Conferences where they give advantages to whoever claimed them, but more on that in a future diary on peace.

Of course, justifying a wargoal increases World Tension.

Tune in next week when we talk about glorious blue France.

Hello, and welcome to the 28th development-diary for Hearts of Iron IV. This time we talk about the things that you have the absolutely least control over in the game, and in real life. ie, Weather and Terrain.

We were not happy with the weather-system in HoI3. It was a complex simulation that tried to work as close to reality as possible. It was basically impossible to tweak to the situations we wanted (like very hot desert areas or cold winter in Russia in ’41), and players disliked it. It was a small performance hog and last but not least – all that effort was tucked away in a mapmode you had to keep checking (so most people did not). So for this iteration of the series, we decided to take an entirely different approach.

Full scripting control
Probability for each type of weather can now be scripted for each strategic region for each month, or a definable period. So for example we can get that hardcore, dirty, Russian mud everyone is craving for the months and locations where it makes sense. For modders out there we made a really nifty tool for setting up these values so its easy to tweak and work with (so when you guys make the Cats of the 4th Reich total conversion I’v been waiting for it will be easy). This means that since we can set everything ourselves we have full control over the gameplay effects we want rather than relying on a complex simulation to get it right.

There are 6 types of basic weather in the game. These directly affect air and navies and land units indirectly (we get to that)

Clear skies

Baseline weather with no modifiers. Just enjoy the sun bro ​:)

Light Rain

Storm

Snow

Blizzard

Sandstorm

Temperature
Temperature is tracked on province level and mainly affects attrition levels. If its very cold or very warm things will tend to break down a lot more often. You’ll want leaders with the Winter Specialist trait to maximize your efficiency in cold weather.

Mud and Snow (so, ok, there is a bit of simulation)
When it rains or snows we keep track of that (so we can show it on the map) but also to keep track of if it has gotten to extreme levels. Very high snow will affect unit movement speed, but Mud is going to increase attrition levels a lot as well as slow you down to a crawl. A smart player will try not to attack (as a wild example) The Soviet Union just as mud season begins or they might find a lot of their panzer divisions bogged down.

Shown on map
Since weather has such a large impact we wanted to make sure it was always visible to the player. Snow/mud and such is shown directly on the map while storm clouds and rain is in a layer above which we fade away the closer you get so as not to obscure unit movements.

Big thunder storm over Russia

Terrain
While we do quite a lot of things at the state-level, we still have terrain defined per actual province. The terrain-system is completely scriptable as in all Clausewitz games, but the terrains in Hearts of Iron IV is as follows.

Plains

Forest

Hills

Mountains

Urban

Jungle

Marsh

Desert

Different types of battalions have either penalties or bonuses in terrain to attack, defence or movement, compared to a generic Infantry. A few examples. Cavalry has a minor -5% attack penalty in most rough terrain, while Mountaineers gets a movement bonus in hills & mountains, as well as attack and defence bonuses.

Unit-specific penalties that combine negatively with terrain penalties, creates some pretty bad situations. ie, attacking a mountain with heavy armor is NOT a good idea.

Next week, we’ll look at factions, and wargoals!