Peasants are used to gather gold and lumber and build buildings.  Build many of them early in the game with most focused on gathering gold.  Make sure they have a whole lot of protection; these gatherers have 30 HP and no armor.  Peasants are trained at the Town Hall.

 

Footmen are the Alliance's level 1 melee soldier.  They have enough HP to take a beating and like it, so use them initially for defending your peasants from Grunts and Axethrowers.  A good idea is to quickly build a blacksmith and spend the meager 300G 300W to upgrade the armor for your footmen, effectively doubling that statistic.  Footmen are trained at the Barracks.

Elven Archers are a pretty pathetic unit.  Their mere 40 HP and no armor make them an easy target for grunts.  Stay away from this unit until you can upgrade them to Rangers.  With both arrow upgrades, Marksmanship, and Improved Bows, they actually become a unit that can survive in the real world.  Elven Archers require and Elven Lumber Mill to be built.  They are trained at the Barracks.

The Ballista packs a powerful punch against enemy builidings.  If your opponent builds lots of towers, send in a couple Ballistas under support  of Knights and there will be no problem.  The upgrades for Ballistas are way too expensive; if you have enough gold to spare for them, you should have spent it on training Knights for an attack.  The Ballista requires a Blacksmith and is trained at the Barracks.

The Knight has HP, speed, and armor which make it the ultimate solution to your Warcraft II problems.  With both armor upgrades, it has eight armor making it ideal for fighting melee units while its speed gives it the edge over ranged units.  The Knight requires a Stables and is trained at the Barracks.

 

The Humans are the only race in the Alliance that is durable.  This upgraded Elven Archer is much more effective because not only does he have those crucial 10 more HP but also the ability to learn Marksmanship and Improved Bows which will give him more range and attack.  Elven Archers are upgraded to Rangers at the Elven Lumber Mill. Rangers are trained at the Barracks.

These Dwarves are very effective against high hit point units, walls, and buildings.  They are very fragile, so it takes practice to learn how to drop their load to make the most damage.  I have found that they are best when taking out Farms and Towers; they are also effective at leveling rock walls and felling trees.  Demo Squads are trained at the Gnomish Inventor.

The Paladin is an upgraded Knight with the ability to cast some spells.  Healing is an excellent spell to use in and out of battle.  Holy Vision is useful; don't even research Exorcism.  It only works on undead.  Use this unit as much as possible.  The Knight is upgraded at the Church.  Paladins are trained at the Barracks.

The Mage has a weak attack but a few of his spells give him vicious abilities.  I have found that you can save a lot of gold by only researching Blizzard and Polymorph.  By combining these two spells and Fireball which he starts out with, a few Magi can wreak major havoc.  Protect him with Paladins since the Mage is fragile.  He is trained at the Mage Tower.

Oil Tankers are essentially Peasants of the sea.  They build Oil Platforms on top of oil spots (darker marks on the water surface) and bring loads of oil to Oil Refineries or Shipyards.  An effective way to cripple an enemy's navy is to cut off its production of oil by destroying Oil Platforms and sinking tankers.  Be sure to protect you own though.  The Oil Tanker is built at the Shipyard.

The Destroyer is an effective naval unit.  It has much more speed and a higher rate of fire than Battleships do.  You can usually avoid damage to your destroyers by moving them when the enemy ship fires.  You Destroyer will take much more damage directly than by area of effect.  Your navies should consist of a few Destroyers.  Elven Destroyers are built at the Shipyard.

Transports are a vital part of the navy for any map that is mostly water.  Ferrying units across the water is essential for attacking enemy bases, but that is the only use for Transports.  They hold six units, so three Transports can hold two groups of nine Paladins.  There is not much to say about these boats.  Transports require a Foundry and are built at the Shipyard.

Those sneaky Gnomes built subs that submerge so only towers, flyers, and other submerged units can see them.  You should probably stick to destroyers and battleships because of not only shore bombardments but battleships can also blast subs out of the water with their Attack Ground ability.  Gnomish Submarines require a Gnomish Inventor and are trained at the Shipyard.

These hulking ships are canned power.  Their slow but strong shots can be avoided by moving ships while the juggernauts fire.  If a sub is harrassing you, use the battleship's Attack Ground are target where the shot is coming from.  Battleboats also have good shore bombardment abilities.  Battleships require a Foundry and are built at the Shipyard.

The flying machine is actually a Gnome sitting on a bicycle with wings.  They have no attack but are extremely fast and have the highest sight range.  Due to their scouting abilities and cheap cost, it is a good idea to train one for finding gold mines and enemy bases or expansions.  The Gnomish Flying Machine is built at the Gnomish Inventor.

These guys actually make Elven Archers/Rangers worth something because they can only be targeted by ranged attacks.  However, it is better just to train your own Gryphon Riders because they can do more than one thing.  Since they are so expensive and have a slow attack, it is better just to make large armies of Knights.  Gryphon Riders are trained at the Gryphon Avairy