Wonders
The useful wonders are Hephaistos' Forge, Colossus, Poseidon, and depending- Athena. Try to pay attention to the wonders your cities go on and build temples on useful wonders. Having multiple temples on the same wonder lowers the cooldown. For the best cooldown results you'll want the wonder at level 5. In addition, theocracy is a useful government for fighting if you have forges. Forge is a must have for fighting and no matter what skill level you are, so long as your opponent doesn't make horrible mistakes you will always lose against a forged army or navy if you are unforged. Check the levels of your wonders before war to make sure you'll have the best wonder levels possible.

The Workshop
Here it is important to upgrade your units. You should do every upgrade you can. However there are some priorities to upgrade first. On frontline and flank units upgrade both the attacks and defense. On longrange units upgrade their attack first. On artillery, wait until you've upgrade most other things. On carriers, bombadiers, gryocopters, and Paddlewheel steamboats upgrade both attack and defense. Units to not upgrade are archers, slingers, and ballista ships until you have upgraded everything else. Keeping your workshop on a crystal island will save time on shipping.

Barracks and shipyards
During a fight you will need to replace units fast. The best way to do so is by having decent level barracks/shipyards in your cities. If you can get one of each in all your cities that is ideal for reducing the training time. A level 13 barracks trains all land units. A level 19 shipyard trains all sea units.

Walls
Walls are a tricky thing. A low level wall hurts you more than it helps you. In addition walls can hurt you on the defense once a section goes down as the enemy will get a free shot at your units that try to fill the block. The main goal of a wall is to buy time. Keeping a low level wall with a spearman buys some time though if you ever station your regular army in the town, a level 1 wall is awful for you. So the biggest thing to make sure is that your wall does not get destroyed in one round. This means you want to upgrade your wall. In the beginning when battering rams are in play a level 6/7 wall is decent. If catapults are in play a level 12 wall is okay. Once mortars are in play you'll want a wall of at least 17 though at 20 the wall can start killing SGs so I personally use that as the benchmark for mortars.
When you can, try to have an overflow battlefield so that your troops are not behind the wall during a battle on account of the disadvantages a wall can bring.

Hideouts
Espionage is big in wars. Having a hideout in your towns is a necessity. Keep your hideouts close to your town hall level. Stationing spies help to reduce an opponent's odds of spying you out however if there's no sensitive information in your city such as troops, lootable resources, or troop movements then you can send spies out from that city to spy out others.

Research
The best fighters are also researchers. Being able to produce the finest units is a military necessity and without lots of good academies that's impossible. Keep researching all the time. One way to boost research speed is by doing experiments too.

Gold Stock
Gold is the most valuable asset you can have and you're preparing your gold stock for war 24/7. Keep a positive income during the peace to create a gold stock. Then in wartime you can build a larger army and go into the red. Also, selling resources before war is always helpful in maintaining a gold stock. During war you'll oftentimes lower production in mills too though academies are usually useful to still keep full. If your gold ever drops to 0 you will lose as many troops as it takes to balance your income to 0. So if you have a large force out of your cities and drop to 0 gold, you will lose much of that force. That is why gold stock is so important.

Resources
It's always good to stock up on sulfur, wine, and building material so that you can rebuild armies and replenish population quickly. However you will most likely gain some of these resources during war so don't keep too much.

Always keep your resources as close as possible to safe levels in the warehouses (2-3 warehouses will help you out there). If you get looted it aids the enemy and your effort in getting those resources goes to waste. If you have lootables when war is announced, stop production and spend spend spend.

Land or Sea
To fight you'll obviously need to build troops and ships but to decide how to build you must ask yourself: Will I devote myself to the ground or the sea? Ground armies have immediate benefits visible such as pillaging and can be used as another form of resource gathering when used effectively. Navies are very useful in locking down an army, defending towns from off-island attacks (1 ram ship is mightier than the largest ground army ever when it comes from another island) and blockading an enemy to make them wither on the vine so to speak. Once you have chosen your field of combat you should gear your workshop upgrades and researches towards that field's needs.

90% of warfare summarized
I like to say that 90% of warfare can be summed up as getting as close as possible to your enemy before attacking. Now you may be asking, well how can I get closer to my enemy? The answer is occupations.
If your troops are on 50:50 and your enemy is on 40:40, sending an attack from 50:50 would give your enemy a lot of warning time with which to prepare for the attack. However if you occupy a town not belonging to your enemy on 40:40 and launch an attack from there, you'll drastically decrease your enemy's warning time and improve your chances of success. Ideal cities/ports to occupy are those with low MSs and not belonging to a strong alliance. Always make sure to the best you can that your enemy will not be alerted of your coming to the island.

When occupying a town/port you intend your troops to return to, always leave a small garrison behind to prevent the owner of the town/port from freeing their town/port and scattering your units when they return. Any lootables you gain from pillaging when originating from an occupied town will give 10% of the reward to the town owner.

Mobiles
Known as mobiles, floaters, or MWCs having one colony that you don't develop as a normal city but instead plant and destroy many times is a valuable tool in warfare when you can use one. Having a mobile colony allows you to shorten your supply lines to speed up pillaging, conduct more piracy raids if you're a pirate, and mitigate the effects of colossus as you troops will be closer to home than they would otherwise be. Mobiles also allow you to have another way of penetrating islands that would otherwise be closed off.

Using wonders
Wonders are a crucial part of fighting and the three wonders which influence fighting are important to use.
Forge: This is used for large battles. Basically you use it whenever you feel you need it. So if an enemy has 10 hoplites, probably not the time to use the forge. But if they have a decent force, time to forge up.
Poseidon: Necessary for any naval fighter. Use it when moving Balloon Carriers are during a battle when you're learning new tactics so that you can send the proper amount of ships into a battle after seeing the round's CR.
Colossus: There are two schools of thought for the colossus. School of Thought 1: Have a level 5 colossus and scatter the entire enemy force. The benefits of this idealogy is that your city stops being attacked however you don't destroy much MS. School of Thought 2: Have a level 4 colossus and scatter only half of the enemy force. This school of thought is for someone that will then proceed to slaughter the half still at your city and then hunt down the other half to slaughter it too. This allows a smaller force to beat a larger force.

There are two things to always make sure you do when you go offline during a war.
1: separate your cooks and tenders from your army/fleet. To do this you can send them on a defend mission. This is so that your army will flee if it's losing a battle instead of being slaughtered and giving the enemy a major damage win.
2: Keep your troops in a safe location. If you can find a place where the enemy will not attack, that is where you should try to store your troops when going offline to limit the chance of your enemy finding your MS while you're offline.

Although there are some units that are better than others there is almost always a time to use certain units. I've explained the special cases with spearmen and slingers. These tips are for pitched battles.

When the enemy has balloons on the field it is time to make sure there are no mortars on the field. Use rams as they are less MS to lose and can last longer.

When the enemy has mortars, SGs are very vulnerable and it is the wrong time to use them as you will lose a lot on damage. Instead it's time to use hoplites.

When the enemy has a level 1/2 wall you are able to shorten their warning time and send hoplites to destroy the wall. However that is only in regards to undefended cities in wartime as otherwise sending a couple rams is cheaper.

The naval battlefield is very easy to understand if you understand the ground field and vice versa. Each battlefield has the same components. There are only different nuances in how things are.

The areas of the battlefield

The Frontline: This is where the heaviest fighting goes on. It is filled first with Flames, then Steam Rams (PWRs), ram Ships, Ballistas out of ammunition, Catapults out of ammunition, Mortars out of ammunition. Flames and PWRs are the only units you ever want in the frontline.

The Flanks: This is an essential area to any combat and if the flanks fall, you're on the path to losing. It is filled with Ram Ships.

The Longrange Battle Line: This targets the front and is necessary. It is filled with Mortars, then Catapults, then Ballistas. Mortars are the best but Catapults can hold their own.

The First-Strike: This is the most essential line of combat to have after the frontline and flanks. It is extremely powerful. It is filled with Rocket Ships, then Diving Boats (Subs).

Carrier-Ship Evasion: This line is like the gyrocopters on land. You only need this when your enemy has Balloon Carriers or if you have Balloon Carriers and your enemy has Paddle-Wheel Steamboats. It is filled Paddle-Wheel Steamboats (PSBs aka Paddlers)

Carrier Ship: These target the opponent's First Strike line. This line is filled with Balloon Carriers.

Support: This line does not show up on the battlefield and can never be destroyed. It supplies morale and healing to your ships.

The Ships

Ram Ships: These ships require now research and are the first ship possible to build and are akin to Swordsmen on land. They take the flank and are necessary.

Ballista Ships: These weak ships have very little purpose and should not be built.

Catapult Ships: These longrange ships can hold their own and are not bad. They are recommended for battles before you have mortar ships. However do not fear if you only have cats vs mortars.

Flame Ships: Flames are akin to hoplites on land. They have great stamina and are strong. They are essential to advanced and early battles. Flame ships will die quickly in wars so always be ready to replace them.

Steam Rams (PWRs): These are akin to SGs on land. They require waving and are powerful at sea. They are essential to combat.

Paddle-Wheel Steamboats: These are akin to gyrocopters on land. You only need them when your enemy has Balloon Carriers or you have Balloon Carriers and your enemy has Paddlers. They only attack Balloon Carriers and PSBs.

Balloon Carriers (BCs): Balloon Carriers attack the first strike. A forged BC against an unforged navy is nearly impossible to kill. They take a long time to travel however so try having a Poseidon when moving these. Otherwise you may as well watch "Lawrence of Arabia" twice while waiting for them to arrive at their destination.

Rocket Ships: These are very powerful ships however they are fragile against BCs. They are gained early on and for most of your early career as a navalist they are strong.

Diving Boats (Subs): Diving Boats are the First-Strike of choice in most cases. They take two rounds to be killed by BCs, field more, and have more ammunition.

Tenders: Tenders are Cooks and Doctors rolled into one unit. They are essential for battles as the heal your ships and restore morale. 10 tenders should be enough to keep 100% morale throughout a battle. Building some more for healing purposes can be good.

Proper Navy Build

In battles flames and rams are what you will go through most. Build your flames in numbers such that you have enough to fill three blocks for however many rounds you think you'll fight. Build your PWRs such as to be able to fill the remaining blocks.

The Most Basic Strategy

Always keep at least one ship in each port. (I prefer 1 Paddler) This limits the effectiveness of off-island attacks without naval assistance as 1 ship can turn away any army.

The Overflow Battlefield

Just as on land there is an overflow field. The only difference with overflow is that it just makes a larger field as there are no walls to overflow over. To calculate overflow at sea
125 + (25 x highest trading port or shipyard level)
Fleets with more ships than the overflow will go into the largest field possible.

Short Summary
Ground armies attack on the ground against other ground units. There are four actions ground units can perform.
Deploy Troops: move troops to another city
Defend Town: Defend another town for a short duration.
Occupy Town: Occupy the town and then use it as a base of further operations. The town owner will get a 10% cut of any pillages you make.

The Areas of Combat

The Frontline: This is the center of the battlefield. Every army needs a frontline. Frontline blocks are filled with units in the following order: Hoplites, Steam Giants, Spearmen, Swordsmen, Slingers out of ammunition, Archers out of ammunition, Sulphur Caribeeners out of ammunition. Hoplites and Steam Giants are the only units you ever want present in the frontline. If you run out of those two units it's usually time to hit the white flag and retreat.

The Flanks: The flanks are on the side of the battle and extremely important. An army without flank units will lose. Without a flank the longrange line of combat (to be mentioned next) will get slaughtered by enemy swordsmen. The flanks are filled with the following order: Swordsmen, Spearmen. Swordsmen are the only units you will want on the flanks. If your flank falls it is usually time to hit the white flag and retreat.

The Long Range Battle Lines: The long range battle line is essential to damaging an opponent's frontline. It is filled in the following order: Sulphur Caribeeners with ammunition, Archer with ammunition, slingers with ammunition. Sulpur Caribeeners are the only worthwhile long range unit for pitched combat.

The Artillery: These units can knock down walls and damage frontline units. This line is filled in the following order: Mortars with ammunition, Catapults with ammunition, Rams.

Air Defense: These units only fight other Air Defense units or Bombers (mentioned next). Gyrocopters are the only Air Defense units. Air defense is only needed when the enemy or you have Bomber present.

Bombers: Bombers attack the enemy's artillery. The only unit they are filled with is Balloon Bombardier.

Support: This line doesn't show up on the battlefield and can never be killed. It's most important task is supplying morale to your troops.

The Units

Spearmen: These are the cheapest units and train quickly. They are extremely weak and have no purpose in pitched combat as fighting units. However they still do have purposes.
1: They can prolong a battle. If your wall loses a section a spearman can make a battle last longer for help to arrive or for you to dispose of your resources. Having 1 spearman is useful for that purpose. In addition building 13 spearmen individually while a battle is going on in your city can prolong the battle too as one will be in each block in the battle. This means that there is one spearman left over at the end of the round and the battle continues. This again is to make the battle longer for help to arrive or to get resources out of your city.
2: Making an overflow battle. When the number of units in a city exceeds the garrison limit, it creates an overflow battle. Enemies can often be surprised when the battlefield size they were expecting isn't present but a much larger field is. This can lead to an excellent first round.
3: Replenishing population quickly in war. In war population is often needed badly and disbanding spearmen recruited prior can replace citizens needed to create your main battle force.
4: Defense system. Stationing one spearman in alliance-mate towns allows you know when that town is being or has been attacked.
5: Pillaging undefended cities. Against undefended cities spearmen have cheaper maintenance and are easy cannon fodder against a wall.

Slingers: Slingers are the first longrange unit you can make. In pitched combat they are, like spearmen, worthless but do have their uses outside of normal battles. Before balloon bombardiers are a common unit you can place one slinger in a town with no other ground defenses but a high level wall. As the enemy tears down the wall, the slinger will stay in the longrange line and makes it so that the enemy has to tear down the entire wall instead of one wall section to win. This can prolong battles to be as long as an hour and gives you lots of time to comes online and save any resources in the city.

Archers: Archers are basically upgraded slingers. However their pathetic strength means that they are not really worth their mettle. The only time you should consider using archers is if you have not researched gunpowder yet (which with a research drive can be done in under a month) and have a decent sized battle to fight where they will provide extra damage on the enemy in a war. (But the extra damage done is quite pitiful in how much it does. Plus in order to get any noticeable benefit the archers have to be upgraded in their attack which is a waste of your crystal as you can get guns which are powerful pretty soon if you focus on research a little.) For regular pillaging however it would be better to have more of other units. Archers should not be considered for use.

Hoplites: Hoplites are tough fighters and go in the frontline. Every army needs hoplites. They can tear down level 1/2 walls without any artillery and as said, are a necessary unit.
......... Spartans are in essence beefed up hoplites and an awesome unit. However they cost ambrosia and the offers for Spartans are limited. Take care of your Spartans.

Swordsmen: Swordsmen take the flank. They are a necessary component to every army. Never underestimate the power of swordsmen.

Sulphur Caribeenrs: Also known as SCs or gunmen, these units own the longrange battle line. They are the only longrange unit you should use.

Steam Giants: These units are very powerful on the frontlines and it takes a lot to bring an SG down. However you need to wave them and when mortars are present on the enemy side it's time to take them out of the frontline. (Further details discussed later in waving.) Make sure to know that these units do not replace Hoplites.

Rams: These artillery units are the first possible to build and need no ammunition. They take three round to be killed by enemy balloons and are therefore quite useful in advanced battles.

Catapults: These are upgrades on rams and cause decent damage. However they do not have much of a place in advanced battles. It takes two rounds for a catapult to die from balloons.

Mortars: These are the best artillery unit but are very fragile. Always protect you mortars which only take one round to die against balloons.

Gyrocopters: These units are on an as-needed basis. Only if your enemy has balloons or if you have balloons and your enemy has gyrocopters should you have these units. They do not fire at any units other than balloons and gyrocopters. Before balloons are a common units it's okay to keep a few of these around just in case but do not go overboard.

Balloon Bombardiers: These units are awesome except for their long travel time. It is quicker to bring a Balloon from another island than to have them travel on the same island. They target enemy artillery and in some cases can save a wall from ever being breached.

Doctors: Doctors heal some units however their healing is not all that strong and they are generally considered a crap unit. It is more cost effective to build more units than to have expensive doctors. However in huge land battles (overflow field and many many rounds) they do save some swordsmen which is a time to consider them but as the units they save are few, their large cost is not truly justifiable.

Cooks: Cooks are a vital unit in your army as the keep the army's morale up to prevent it from fleeing. Each cook raises morale by 1%. 30 cooks should keep your army at full morale indefinitely no matter the circumstances.

Proper Army Build

Now that you know what the units are, the question becomes how to make your army. One thing to always keep in mind is a Flank-Frontline ratio. You should build one sword for every hoplite and three swords for every SG.
With proper waving, 420 SCs is about the most you'll ever need and even that number gives you some leeway.


The Overflow battlefield.

The overflow battlefield occurs when the defending army goes over the garrison limit. This means that the battle takes place outside the wall of a city (which will reappear when the defending army goes under the garrison limit) and is the largest field possible.
Garrison limit on land is calculated as
250 + (50 x (town hall level + town wall level))
If the number of units defending exceeds that number the battle will become an overflow.

A strategy with overflow battlefields that can be used is to exhaust your enemy's artillery ammunition and then bring the battle out of overflow into a battle where the walls come into play and being able to hold indefinitely.

At sea waving still applies however there is a difference from land. I'll first give the simpler aspects and then the more complicated aspect.

Diving Boats: Diving boats can be saved from dying by BCs by waving in some each round. Even just 10 new Subs each round goes a long way. Doing so also replenishes ammunition.

Ram Ships: Waving in new Ram Ships each round helps to reduce your Ram Ship losses.

Longrange Ships: As on land, longrange ships can be retreated out and waved back in to keep up the ammunition supply.

PWRs: Like their SG counterpart of land, SGs can lose stamina and waving in new ones is important.

The rule of three flame blocks: This is the most complicated but also most important technique at sea. The idea is that, excepting the smallest battlefield, it is best to have three blocks of flame ships with PWRs filling the other blocks. With forges and a perfect battle the middle three blocks will be annihilated and losing three blocks of flames is less damage than three blocks of PWRs. This means that each round you should send in enough flames to fill three blocks on the battlefield.

Section 10: When To Use Certain Ships

Rocket Ships: These are normally bad to have as BCs kill them in one round which is a lot of damage to suffer. However when the enemy has a full frontline of PWRs and no BCs, it is better to use Rocket Ships than Diving Boats.

Section 11: Glossary

TH: Town Hall
CR: Combat Report
Overflow: When the number of defending units exceeds the garrison limit.
SG: Steam Giant
Gyro: Gyrocopter
SC: Sulphur Caribeener
Gunman: Sulphur Caribeener
PWR: Steam Ram
Flame: Fire Ship
BC: Balloon Carrier
PSB; Paddlewheel Steamboat
Paddler: Paddlewheel Steamboat

Waving is the most important thing in understanding combat and becoming a good fighter. Anyone can send their whole force forward with one click but waving a skill that takes time to master. The basic summary of waving is that instead of sending your entire force, you send parts of you force ahead to fight. You also recall some waves while sending new waves in. Waving requires a lot of action points in larger battles. Some units require waving. Other don't but are still helped by it. Waving units replenishes their health and can help reload them. Note that when units are white-flagged it takes 1 hour + travel time before the can be used again.

Hoplites and Swordsmen: Sending in new ones of these each round is not essential but over the course of a long battle will save some of them.

Sulphur Caribeeners: If you send in some with the first wave and then send in later waves of SCs with enough to last 6 rounds you can white flag one wave when it is getting low in ammunition and bring in the next wave to have SCs for the whole battle without having to build exhausting amounts. 420 SCs should do the job on the largest battlefield. 84 for the first wave. 168 for another wave to last 6 rounds and another 168 to bring in when the other 168 wave is being retreated.

Steam Giants: Steam Giants are powerful units, when they have stamina. They lose stamina quickly however and therefore waving SGs is necessary. To wave SGs send in a full front of them each round. Depending on a situation, sending in less than a full frontline of SGs can work. When you run out of SGs to keep sending in or run out of Action Points (excepting one) it's time to send in hoplites.

Artillery: To limit losses to balloons, try to wave in new rams on such battlefields. In addition, retreat mortars when balloons are present on the enemy side.