Welcome to another development diary for Europa Universalis IV and today we focus on warfare. Yes, you knew this dev diary was coming, didn’t you? It’s really quite difficult to play the game without understanding how the armies work.Warfare is one of the most important aspects of Europa Universalis IV, and over the almost 400 years of gameplay, armies and navies will be your prime instruments of power when you go to war. You need to be aware of the different units of your armies and their strengths and weaknesses.So, it is time to build some armies and go to war! In times of war, you will have to raise and maintain armies and fleets, conquer nations and project your power onto the world. You see them standing, moving and fighting on the map.Battlefield casualties and general attrition will naturally reduce the number of men or quality of ships available to you as you play, but armies will be slowly reinforced and navies in a safe port will slowly be repaired. As you upgrade your technology, you will unlock different types of these units, each with different offensive and defensive characteristics. Some have attributes that favor the attack, some favor the defense, and others are suited for a more balanced approach. Each approach has its advantages and disadvantages depending on your circumstances, and it will be up to you to decide what kind of army you want.Just as in earlier Europa Universalis games, land units are divided into infantry, cavalry and artillery. As you move through the ages, your armies will evolve from men-at-arms and armored knights to advanced musketmen and dragoons, and everything in between. The specific types of unit available to you, and its offensive and defensive abilities, are also dependent on your culture. Asian countries can get samurai cavalry, for example, but you won’t find these guys riding around Spain unless you send them there.You select your preferred unit type of your land units, as you discover them through technology. This interface allows you to select the focus of your military forces. Each unit you build represents a force of 1000 men.Infantry will be the bulk of your army. They are your cheapest units, and don’t take long to recruit. Your cavalry are the force you rely on in a battle to hit the flanks of an outnumbered enemy or chase down those that can’t stand against you. They cost about double what an infantryman does. Artillery only become available at Land Technology Level 7 (Limber) and they are most important for their firepower on the battlefield and their effectiveness during sieges.When you build your armies, keep in mind that an army that is more cavalry than infantry loses the “combined arms” advantage. Cavalry could be very powerful and fast at times in this era, but rarely outnumbered foot soldiers on the battlefield.In the military menu, you can see four columns with data on the land units. First there is the power, second the ability during fire, third is ability during shock, and finally the number of regiments you have of that category.There are four types of ships: heavy ships, light ships, galleys and transports. Unlike armies, each construction represents individual ships and have a strength measured in a percentage – a ship at 100% is in perfect health. Ships take damage in battles, of course, but also if they are in the open sea for too long. (This is naval attrition.) Ships only repair when in port.Each naval unit has characteristics, just like army units. There are no longer any separate fire/shock values per ship type, as a ship-based gun is basically a gun. However, every type of ship has a different number of cannons, and a different hull size. There are also ideas that improve your ships ability to fight, or as we call it, the ships’ power.The four different ship types have different purposes. Your main battle fleet will be composed of heavy ships (carracks, galleons, etc.). Light ships (barques, caravels, frigates, etc.) have better speed and are OK in a fight but will mostly be used to protect and project your trade power. Galleys (and later galleases and chebecks) are designed for fighting in inland seas and enclosed bodies of water. Your transports (cogs, flytes, merchantmen, etc.) are, as the name suggests, your lightly armed vessels intended to move troops across the water.In the military interface, ship types have four columns, first there is the power, second the amount of guns, third is hull size, and finally the numbers of ships you have of that category.Any military situation calls for extensive knowledge and leadership, and, for a monarch like yourself, how to choose which of the leaders at your service will serve what purpose in the war you just happened to find yourself in. (Clearly this war is not your fault.)Though you can always put your monarch or a mature heir at the head of your army, you will hire most of your leaders from the general population. You can recruit generals, admirals, conquistadors and explorers as leaders. Generals and conquistadors, as land leaders, cost you 25 Military Power. Admirals and explorers, as naval leaders, cost you 25 Diplomatic Power. Once you’ve hired a leader, it can be assigned to lead any army or naval unit. As expected, generals are used to lead armies and admirals are used to lead navies. Assign conquistadors and explorers to units you wish to send far away or to uncharted lands – these are the only units that can venture into unexplored parts of the map (those sections covered by a white fog).The skill of a leader determines how good he is at performing different strategies and tactics in combat. Leader skill is partly related to your nation’s military or naval tradition; countries with a history of warfare will be more likely to notice these talents among soldiers or general citizenry.The four different attributes of leaders are scored from 0 to 6. “Fire” is their ability to direct the use of gunpowder or missile weapons. “Shock” measures how well the leader is at assaults, charges, whatever happens when ranged combat turns to man-to-man action. “Maneuver” is the ability of a leader to move his troops through land safely and get his forces into the right position for battle. Finally, the “Siege” attribute is most important for quickly taking down enemy cities. Paying close attention to these may be the difference between defeating an army twice your size or getting crushed.Every leader (except your current ruler or heir) costs one military power each month to maintain. This puts a soft cap on the amount of leaders a nation can have at the same time. This also means that a monarch with low military skill and a poor selection of military advisors could find himself running a deficit in military power if he has too many generals. If you find yourself running low on military power, you can always dismiss your leaders, but this means you lose their services permanently.Every country has its own pool of mercenaries which replenishes over time, but the number of mercenaries you have already recruited impacts how many there are available for you. This isn’t an endless pool of soldiers for you to draw from. There are ideas that increase the size of the pool, as well as reducing the maintenance or cost of mercenaries. There are only mercenaries on land – you can’t hire renegade naval forces to fight for you.Mercenaries do count against your land force limits – they are not a way to get around the costs of having to field an army that is already stretching your budget. But they do have a couple of advantages in certain situations. First, they are faster to recruit, so if you have seen your main force destroyed but can afford to get new men, mercenaries will get you back in the fight faster. Also, mercenaries fight just as well as regular troops and can be led by your generals and conquistadors if necessary. The best part is that they don't cost any manpower to reinforce, so while they fight and die, you can rebuild your own population for a later war. They are a vital part of any nation’s armed forces, and rich countries can benefit from them quite a lot.ps. And in case you haven´t read this yet: