Execution
Damage Types
Certain types of attacks are better suited against certain types of units. Specifically, a unit may inflict damage in one of three different ways. See the specific unit descriptions elsewhere for further information on a case-by-case basis.
Normal damage means the unit in question will always inflict what is indicated in its onscreen status bar with each attack against every opponent.
Explosive damage deals only 50 percent of its standard damage against units designated small in size and 75 percent damage against medium-sized units. Explosive damage is dealt in full against large units. The Zerg Hydralisk is one such unit that attacks with explosive damage. While it will inflict its standard 10 points of damage against a large target like a Terran Siege Tank, it will only inflict five points against a small unit like a Terran Marine. It will inflict seven points of damage per attack against medium-sized units, like enemy Hydralisks.
Concussive damage is 100 percent effective against small units, 50 percent effective against medium-sized units, and only 25 percent effective against large units. But three units deal concussive damage: The Terran Firebat, Ghost, and Vulture Hoverbike. A Ghost agent typically inflicts ten points of concussive damage with his C-10 Canister Rifle and will deal full damage against small units like Zerg Zerglings and Protoss Zealots. He will inflict just five points of damage against medium-sized Hydralisks and enemy Vultures, and a mere two points of damage against large units like Zerg Ultralisks or Protoss Scouts. Concussive damage is, for all intents and purposes, entirely useless against large enemies.
You must memorize those units who attack with explosive or concussive damage and remember to deploy them accordingly, taking heed not to engage them against enemies who are heavily resistant to their attacks.
Of further note, certain types of units deal damage to a small area, injuring the target as well as any adjacent foes. Those units who inflict splash damage are also indicated throughout the unit guide in this volume. Some types of splash damage attacks, like that of the Terran Firebat and Protoss Reaver, are not harmful to friendly forces adjacent to the enemy. On the other hand, the splash damage caused by a Terran Siege Tank in siege mode is just as dangerous to friendly units near the target as it is to the enemy.
Next: Air Power vs. Ground Power and The Lifeline - Your Gatherer Units 
