Command & Conquer: Red Alert 3/Allied Strategies

Allies vs Empire
The Allies are a well balanced force in Red Alert 3. A strength of the Allied forces is clearly their air superiority. One strategy is that of the Vindicator rush. With the ability to build these aircraft very early in the game, rushing to build an  airfield as soon as possible and blitzkrieg-ing your enemies is a  sure recipe for a early victory. This is really a base-killer when facing the Empire as their early anti air defenses are weak at best. This strategy is not as useful against the Soviets. This make sure you don't fully neglect land defenses because you never want to leave your base fully undefended. Also make sure your Empire opponents haven't snuck a Nanocore to the sea where he starts building a secret navy base that will grow to challenge and haunt you in the future.

One more thing to be aware of is that the Empire will attack your Prospectors with the Jet Tengu and its transforming features.

Allies vs Soviets
The Soviet advantage lies with their early vehicles, the Terror Drone and the Sickle. The Terror Drone has the ability to cripple your economy for a measly 500 credits, by disabling or destroying your Prospectors. The key to countering this is walling in the path between your refineries and their respective ore nodes. Sickles can be devastating to your infantrydue to their machine guns and the Flea Jump. If you are intending to use infantry, never bunch them up and use the Scatter (X) key when necessary.

It must be noted that air sorties with Vindicators are not an efficient way to deal early-game strikes against a Soviet opponent due to the early availability of Flak Troopers and Bullfrogs.

One strategy that is effective is to produce 2 Multigunner IFVs and put an engineer into each of them. These vehicles then become "mobile repair units". Always produce at least 2, not just one, as they can then repair each other. 5 Guardian Tanks, 2 Engineers-Multi-Gunners, 3 Rocket Troops into a Multi-Gunner. This group of 10 can be used to rush an enemy base. The Guardian Tanks will form up front, and take the hits while the repair carts will keep repairing them. (Similar to the Starcraft Terran strategy of Marines+Medics)

Allies vs Both
The Chronosphere can be used as a directly offensive weapon - you can use it to destroy enemy land units by teleporting them into the water, or naval units by teleporting them onto land. Amphibious can be destroyed by teleporting them into buildings.

A highly efficient way to apply pressure on an opponent early in the game is to load a Riptide ACV with 5 Javelin Troopers, or two such Riptides if your economy allows it. The Riptide can handle a few Infantry, while the Javelins can take out buildings and vehicles (remember to watch out for Sickles if facing a Soviet enemy!). Focus on production structures and Ore Refineries. Coupled with 2 or more Multigunner IFVs (possibly with Peacekeepers inside), this force may be enough to cripple the opponent for the remainder of the game. Don't forget to replenish your forces, as necessary.

If the initial strike fails, assess the impact of your attack. If your opponent will take some time to recover, try again. Otherwise, quickly reach Heightened Clearance and use Guardian Tanks in combination with a similar force mentioned above.

As mentioned before, the Allies possess a well balanced force with some exceptional examples. The Peacekeeper is arguably the best "grunt" unit of the three factions, the Hydrofoil is undeniably the best ground-to-air unit, with the added bonus of the weapon jammer. The Mirage Tank, though the weakest Tier 3 tank in the game, is the cheapest, and the easiest to conceal.

Engineers in Multigunner IFV Strategy 1: Have a few Engineers in your Multigunner IFV's so they can repair the vehicles as you attack. So the typical strategy is some Guardian Tanks, some IFV's with Javelins in it, and some IFV's with Engineers in it. Also have some Javelins with you. Set them to destroy enemy units only, and not buildings. Once you are next an enemy building, have the engineer jump out and capture that building. Engineers have no protection, can't defend themselves, and walk slowly. In this way, they can do double duty. They repair your vehicles when you have the engineers in IFV's, are transported more safely, and with this strategy, you can overrun a small base quickly. When your engineers are gone, have the extra Javelins jump into the IFV's and take over. One of the best buildings to capture are the Super Reactors, as they almost certainly will make the Russians go low power and give you a lot of power at the same time.

Engineers in Multigunner IFV Strategy 2: You can also use Engineers+IFV's to quickly repair damaged buildings. When your partner is attacking, you can send a few to help them out.

Inchworm Javelin Strategy: If you are in a heavily citied area, then you can build a lot of Javelins and put them into multiple buildings. Fortify 4~5 buildings close to each other. This will help them cover each other. Once the threats have been neutralized, eject the Javelins who are furthest away, out of the building and move them to the next building. Slowly inch your way up to the enemy's base parameter. Use the Javelins in buildings to form a blockade. Also, if you are playing solo and your partner is the computer, consider putting a few Javelins into buildings by their base, because they normally don't.

Top Secret Protocols
The surgical strike works great on units, but poorly on structures. If the computer repairs its' structures, or against a human opponent, don't waste the surgical strike on a building unless it's already hanging by a thread. It is much more useful taking out an anti-air structure or heavy tank.

The time bomb cannot be placed directly on top of a structure or unit, unlike air strikes or satellite blasts. It is a chronosphere-transported unit itself, and must be placed in the space between buildings and units. It is also vulnerable to being targeted and destroyed by enemy units, so beware of placing it beside an offensive force run by the computer. A human opponent may not react in time to attack with their units, but the computer is pretty good about it.

The Chrono Chasm is both an offensive and defensive power. On one hand, it can be used to stall an attacking force if timed and placed correctly (though, the Cryoshot is more effective for this as you can destroy the frozen units easily). It can also be used to disable your own structures in the most dire emergencies. On the other hand, it can be used to stop the countdown on enemy superweapons, disable closely grouped power plants or a Super Reactor, or to phase out any defensive structures preventing you from disrupting your opponents economy.