Here are a list of Allied units that appear in Red Alert.
Infantry
Rifle Infantry - Basic Allied rifle infantry. Their M16s are mostly effective against other infantry and armor (when in large numbers). Engineer - Engineers are deployed onto the battlefield to capture enemy structures or repair one's own. They are unarmed and must be protected by other combat units. Rocket soldier - Infantry units equipped with M72 LAW rocket launchers, Rocket Soldiers are slower than regular Rifle Infantry but are more effective at destroying enemy armor and aircraft. Medic - Battlefield medics have the ability to heal friendly infantry units but cannot attack enemy infantry. Spy - Spies are covert infantry units that are disguised as enemy soldiers and can infiltrate enemy buildings. You can find out how much money your enemy has, what units they are building, and how many units they have. Careful consideratiorrn should be made in that attack dogs can discover them. Thief - Thieves can steal credits from enemy ore refineries and silos (1/2 the credit will be stolen). Tanya Adams - A commando unit for the Allied forces (and Soviet in skirmish), Tanya is armed with M1911 .45 handguns and plastic explosives. Besides being able to tear through groups of enemy infantry, she can also destroy bridges and enemy structures. Field mechanic (Aftermath Expansion Pack) - This unit is able to repair any damaged vehicles that are nearby or ordered to. While repairing units at a bit slower rate, Mechanics have the advantage of mobility and their use is free (apart from the cost of training them, of course).
Vehicles
Ranger - Fast and lightly armored, this unit is ideal for quickly scouting out an area. Used as a support unit for an infantry squad, the Ranger can soften up the enemy before a direct confrontation occurs. Mobile gap generator - The mobile version of the Gap Generator functions in much the same way the stationary one does. Although it projects a smaller gap field, you can hide several units under its cover, blocking the enemy from seeing what you're sending against them. Anti-tank minelayer - The Mine Layer's chassis is similar to that of the APC, however it uses mines that trigger when a vehicle runs over them. It carries five mines but can be resupplied with more from the Service Depot. Ore truck - The Ore truck is a heavily armored vehicle designed to collect ore or gem stones and bring them back to its owner's refinery. It is unarmed and slow but compensates for this with heavy armor. MCV - The Mobile Construction Vehicle allows creation or expansion of a base. Although expensive, the MCV is useful to have around if the original Construction Yard is destroyed or captured. As with any other construction facility, the more of them you have, the faster construction will proceed. APC - With the Armored Personnel Carrier, the Allies can transport up to 5 infantry units quickly across land. As it is a tracked vehicle, the APC is the lightest unit with the ability to crush Sandbag and Barbed Wire barriers. The turret mounted M60 helps keep infantry at bay while it goes about its mission. Light tank - The standard Allied Tank. Fast, with decent armor, the Light Tank works well in mixed groups, and also in large divisions. What it lacks in firepower, it makes up for in speed and rapid fire. Medium tank - This higher-grade Allied Tank is just as well armored, faster, and less costly than the Soviet Heavy Tank, though armed with only a single barrel. Used in groups with Light Tanks, the Medium Tank can draw fire while the Light Tanks destroy the threat. Artillery - Very effective, if somewhat inaccurate, Artillery can devastate infantry and structures from afar. Its slow speed and light armor requires that it be protected. Radar Jammer - This unit allows the commander to jam the radar structure continuously and automatically if the unit is close to a radar center structure. Demolition truck (Aftermath Expansion Pack) - This vehicle carries a small low yield nuclear bomb that is detonated when the vehicle is destroyed either by command order, low hit points to point of destruction, or chronoshift. Chrono tank (Aftermath Expansion Pack) - Once charged, this tank has the ability to chronoshift itself to any place on the battlefield that has been explored. The unit cannot take much punishment but, to compensate, has average speed and powerful missiles.
Aircraft
Longbow helicopter - The Allied Longbow attack helicopter is loaded with Hellfire missiles, allowing it to destroy armored targets with ease. Used in conjunction with naval or ground attacks, the Longbow is an ideal support aircraft, able to rapidly inflict additional damage to a target - usually with little to no return fire.
Transport - This naval unit can transport up to five units, be they vehicles or infantry. Used in conjunction with other naval support, it can lead a devastating amphibious assault. Gunboat - The fastest and lightest of the Allied naval vessels, the Gunboat is good at scouting naval routes, and detecting Submarines before they can cause any mischief. Its depth charge launcher will automatically fire at any Submarines detected nearby. Destroyer - The Allies' mid-level naval vessel, the Destroyer is effective against land, air, and sea based threats. Its fast-firing Stinger missiles can hit air targets easily, and can also decimate nearby ground targets. If it detects a Submarine, its dual depth-charge launcher ensures that the Sub will be rapidly taken out of commission. Cruiser - Slow moving death. What the Cruiser lacks in speed, it makes up for in firepower and range. Able to lob destruction onto targets at incredible distances; though inaccurate, it can decimate an enemy base in minutes. A favorite target of Submarines, these ships have no naval defenses, relying on the faster moving Destroyers and Gunboats to protect them.