General Strategies and Tactics

Regarding Cloaking and Cloak Detectors
Little is as frustrating as sending an indefensible strike force at the enemy, only to be assaulted by an invisible enemy. Avoid this situation by sending a cloak detector unit with every major attack if you feel there is any chance of cloaked opposition. Each species has exactly one cloak detector unit. These are the Terran Science Vessel, the Zerg Overlord, and the Protoss Observer. Zerg Overlords and Protoss Observers are inexpensive, so in most cases, it will not be a problem for you to send one along with your fighters. The Terran Science Vessel is rather costly, on the other hand. If you cannot afford to order it into open combat, you can substitute for it with the Scanner Sweep ability made available after you add a Comsat Station to your Command Center. A Scanner Sweep will reveal all cloaked enemy units in the area for several seconds.

The Terrans rely on cloaked units more so than the other species. Their Wraith fighters and Ghost agents can be devastating if they remain undetected, and the deadly Vulture Spider Mines are invisible to the enemy unless they pass within a cloak detector's field of vision. The Zerg have no cloaking ability, but most of their land units may burrow underground. Use cloak detectors to reveal them. Protoss Observers are cloaked, and the powerful Protoss Arbiter, while perfectly visible itself, casts a cloaking field around all friendly units within a large radius.

Cloaked Wraith starfighters lead the attack against a rival Terran headquarters after Marines eliminated its perimeter of Missile Turrets

Each species' anti-air defense structure doubles as a cloak detector. The Terran Missile Turret, Zerg Spore Colony, and Protoss Photon Cannon are all equipped with sensors designed to detect otherwise invisible units. Because none of these defensive structures is notably powerful, they are all primarily useful for their cloak detecting properties.

Cloaked enemies may still be identified by the slight shimmering effect of their cloaking fields. However, your weapons cannot target them directly unless a cloak detector reveals them. Cloaked units may still be attacked by special abilities, however. Just target the area where their attacks originate or identify the shimmer and target that point. A Protoss High Templar may damage or destroy the invisible forces with his Psionic Storm. A Zerg Queen's Ensnare ability not only slows all units within the target area, but the green spores also make otherwise cloaked units visible to your forces. Likewise, a Zerg Defiler's Plague will reveal cloaked units even as it drains them of their hit points. Cloaked units may cause a great deal of trouble for one who is unprepared to deal with them, but are not so problematic if you take precautions.

The High Ground Advantage

The Bunkers on higher ground rain death on the enemy Bunkers below

There are several reasons why a ground unit on higher elevation than an enemy ground unit is at an advantage. The unit on low ground cannot see the unit on high ground through the fog of war, unless the unit on high ground attacks it. The unit on high ground receives a bonus to its field of vision, thus letting it see farther than is typically possible. And finally, the unit on low ground has a 30 percent chance of missing the unit on high ground with its attack. Thus, should two equivalent units fight across elevation (for example two rival Terran Goliaths), the unit on high ground will always win, since the unit on low ground will occasionally miss its mark while the unit on high ground will not.

For all these reasons, it is advantageous to seek out a position on higher elevation. Flying units are not affected by the elevation of their terrestrial targets, so often times the best means of striking at an enemy firmly planted on high ground is to attack him from the sky.

Next: The Missions Guide - Terran, Zerg, Protoss