Time for another friday diary! Today I'll be talking about one of the biggest changes in Hearts of Iron IV compared to the previous titles: Battle Plans.When I started looking at what direction to take HOI4 for unit control and provinces I first looked at HOI2 and HOI3 to see what worked well and what didn't.+ Fewer provinces making full manual control always possible- Few provinces leads to a lot less cool encirclements and removes a lot of interesting tactical gameplay+ Lots of provinces allowing encirclements and interesting gameplay+ HOI3 had a purely cosmetic battle plan drawing system, and still people used it - because drawing plans feels natural in a strategic wargame like this and it feels right to see and makes showing things to others in say AARs easier.- Lots of provinces means manual control everywhere can be overwhelming, difficult to manage in multiplayer and annoying in areas where you "don't care so much".- You could hand over control to HQ units run by AI for you and give them objectives. The problem was that effectively you had very little control, and features that play themselves are generally not a good idea. Giving up control also isn't something most players like to do.For HOI4 we decided we wanted to attempt the best of both. Keep the high province count, always allow manual control override, enough tools to automate parts that didn't matter and control and feedback when managing lots of units at the same time so you would not be surprised by the system doing things you didn't tell it. The system is specifically not allowed to be clever, that is the player's job, so if you tell it to suicide into the maginot line it will say it thinks it's too risky, but do it anyway.The battle plan system in HOI4 lets you draw plans on the map which are followed by assigned divisions, but at any point you can go in and reassign things or issue manual overrides. The player's role is then basically to draw up high level plans and to watch for opportunities and situations to take advantage of (such as small encirclements, or prioritizing fighting a certain enemy, or cutting off someone's retreat). Generally the strategic situation will change over time, so while you may have prepared a longer plan expect that you will need to improvise and adapt parts as you go or break off a group to manage some emergency, or particularly stubborn enemy section.Battleplans are controlled for each Army and you have several tools for drawing them:Used for planning naval and paratrooper invasions. We will cover these in a diary in 2 weeks or so.Used to assign divisions in an army to a frontline. You can either assign to the whole frontline with a nation by clicking it, or click and drag to assign just a part of it. Having an assigned frontline is required for making offensive plans because you need to know where to attack from.This tells divisions assigned that you want them to advance along their axis of attack (represented by an arrow that you can bend and adjust as you want) from their assigned frontline to the offensive line. You can chain several of these together if you want as well.Offensive lines and frontlines may also be overlapping. I prefer to assign a big front line of infantry to a frontline with a broad attack plan, and then manage my panzer divisions or other breakthrough units along smaller sections of that front and with a much narrower offensive line. In my barbarossa plan above Guderians panzer divisions are operating in this way together with von Rundstedt's infantry.When you have drawn an offensive line you can hover mouse over its arrow and the game will show you a map highlighting step by step of how your units would move to take this area (the green strips in the picture below)This lets you paint a line useful both for say setting up a defensive position behind a river or other position (for example a coastline). They are very useful for falling back in a controlled manner as well by reassigning your attackers to it they will instantly rush back and hold that point instead (I do recommend leaving some defenders to slow the enemy during your retreat).For this order you give the army an area of responsibility instead of a frontline. Divisions will spread out to guard the most important provinces, keep resistance down, or take back provinces as long as it's pretty safe. So useful for home defense, or mop-up of areas.Lets you quickly reassign divisions between frontlines, attack orders or command groups. Super useful and you'll be mostly accessing it by holding down the Control key.Lets you adjust any part of a plan by clicking this or holding down the Alt key. You can do things like changing the axis of attack, reshaping offensive or fallback lines.You can of course delete whole plans (just right click), or parts of plans (click on the plan on the map).Battle plans are not just a way of controlling your units, they also come with advantages if you put the time in to prepare them. The longer you prepare a plan the more bonus is acquired up to a point that depends on your doctrine. For example Mobile Warfare Doctrine gives you faster planning but you can only plan to half the level of a player using Grand Battleplan (Even units given manual order as part of a plan will gain this bonus by the way). As you progress along the plan the bonus slowly goes away, so you may want to time it to coincide with a good defensive position for regrouping. There are also certain leader traits that improve planning and can create powerful combos with the right doctrine.Next week we will take a deeper look at Britain.