The G.I. is the standard Allied infantry unit. Slow and cabable of only light damage.  Deploying a G.I. will cause him to deploy into a heavy machine gun platform which offers increased range and power, but no ability to move.

Engineer

Although unarmed, the engineer can be used to repair bridges, steal enemy buildings, repair your own buildings or occupied civillian structures and capture neutral tech buildings.

This is the aerial assault versin of the simple allied GI. Armed with a powerful weapon and strapped into an equally powerful jetpack, the rocketeer hovers over the battlefield.

Spy

The spy is a stealth unit used by the Allied forces to gain an advantage over their foes.  Rather than attacking enemy units, the Spy who targets an enemy changes his appearance to that of the enemy unit.

The most versitile infantry unit for the Allied forces is Tanya. About as fast as a typical GI, Tanya also has the ability to swim across rivers and oceans.  While not that powerful against vehicles, Tanya's powerful weapon kills off enemy infantry units with a single shot.

Attack Dog

Attacks guys.  Devastating against infantry. Does nothing against vehicles and buildings.

Chrono Legionaire

This guy teleports around the map. Good unit. Also removes enemies off the map.

Grizzly Battle Tanks

The standard tank for the Allies.  The Soviet rhino tank is stronger though.

Shoots missiles. Put different types of infantry into it and see what happens to it.

Great plane which is one of the best.

Carries infantry across the screen.

Great Vehicle. I love this one. Have a group of these and see what happens.  Shoots a very powerful laser at targets.

MCV

Mobile Construction Vehicle. Heart of starting a base.

Main source of getting money.  Unlike the Soviet ore miner. The allied chrono miner, chrono's back to the refinery when its full.

Hovercraft transport.  This will transport all land vehicles.

Backbone of the Allied Navy.

Sea-land navy naval ship.  Protect the rest of your naval ships with this.

Has three planes that reproduce automatically, free of charge when one of them gets shot down.

Dolphin

A little odd.  Not worth getting these in some of the missions.