*This page last updated: 19 February, 2012 12:09 PST.

General Notes

Sources of Unit Experience

Units gain experience from surviving combat, whether attacking or defending. Note: once a unit has 30 XP, it cannot gain any more experience from fighting Barbarians. Having the Military Tradition social policy (under the Honor tree) doubles experience gained from combat.

Unit Promotions

"Your units earn promotions through combat, and also from being constructed in cities with Barracks or other military buildings. Promotions can dramatically improve a unit's combat ability or increase its movement or its healing rate. A unit with a lot of promotions is extremely valuable -- use them wisely in battle and always upgrade them when possible."

"Unit Types" are those units or classes of units that this promotion has been seen on; it's not definitive.
"Requires" lists appear to be "OR"... Logistics appears to require Accuracy 3, OR Barrage 3, OR Targeting 3, OR Bombardment 3

Embarkation

Unit Types: All Land Units, Helicopter Gunship
Notes: This is the promotion that allows a land unit to embark on water. It can be earned like a normal promotion, but it is automatically given to all units following the research of the Optics technology. Civilian units such as Workers can also have Embarkation. Note that a unit must be in friendly territory to receive this promotion.

Medic

Unit Types: Longswordsman, Knight, Musketman, Horseman
Notes: Restores 1 hit point per turn to itself and all adjacent friendly units.

Heal Instantly

Unit Types: Any
"Heal this unit completely. (Doing so) will consume this opportunity to choose a promotion."
Notes: This is not a regular promotion, but the ability of (any) unit to forgo a promotion in order to completely heal itself.

Drill 1-3

Unit Types: Melee, Mounted, Gunpowder
Notes: Bonus for fighting in ROUGH terrain.
Drill 1: +20% Combat Strength when fighting in ROUGH Terrain (Hills, Forest or Jungle).
Drill 2: "+20% Combat Strength when fighting in ROUGH Terrain (Hills, Forest or Jungle)." Requires Drill 1.
Drill 3: +25% Combat Strength when fighting in ROUGH Terrain (Hills, Forest or Jungle). Requires Drill 2.

Shock 1-3

Unit types: Melee, Mounted, Gunpowder, Armor
Notes: Bonus for fighting in OPEN terrain. 
Shock 1: +20% Combat Strength when fighting is OPEN Terrain (NO Hills, Forest, or Jungle).
Shock 2: +20% Combat Strength against Units in OPEN Terrain (NO Hills, Forest or Jungle). Requires Shock 1.
Shock 3: +25% Combat Strength against Units in OPEN Terrain (NO Hills, Forest or Jungle). Requires Shock 2.

Accuracy 1-3

Unit Types: Ranged
Accuracy 1: "+20% Ranged Combat Strength against Units in OPEN Terrain (NO Hills, Forest or Jungle)."
Accuracy 2: +20% Ranged Combat Strength against Units in OPEN Terrain (NO Hills, Forest or Jungle). Requires Accuracy 1.
Accuracy 3: +25% Ranged Combat Strength against Units in OPEN Terrain (NO Hills, Forest or Jungle). Requires Accuracy 2.

Barrage 1-3

Unit Types: Siege, Archery
Barrage 1: "+25% Ranged Combat Strength against Units in ROUGH Terrain (Hills, Forest, Jungle)."
Barrage 2 +25% Ranged Combat Strength against Units in ROUGH Terrain (Hills, Forest, Jungle). Requires Barrage 1.
Barrage 3 +25% Ranged Combat Strength against Units in ROUGH Terrain (Hills, Forest, Jungle). Requires Barrage 2.

Siege 1-3

Unit Types: Siege, Archery, Air, Mech Inf
Siege: "+25% Combat Strength VS Cities"
Siege 1 (Air): +25% Combat Strength VS Cities.
Siege 2 (Air): +25% Combat Strength VS Cities. Requires Siege 1.
Siege 3 (Air): +25% Combat Strength VS Cities. Requires Siege 2.
Notes: It looks like Siege 2+ are reserved for Air Units.

Bombardment 1-3

Unit Types: Naval
Bombardment 1: +20% Combat Strength VS Land Units. 
Bombardment 2: +20% Combat Strength VS Land Units. Requires Bombardment 1.
Bombardment 3: +20% Combat Strength VS Land Units. Requires Bombardment 2.

Range

Unit Types: Air, Ranged
"+1 Range for Ranged, +2 operational range for Air." Requires: Accuracy III, Barrage III, Targeting II, or Bombardment II.

Logistics

Unit Types: Ranged
Required Promotions: Accuracy 3, Barrage 3, Targeting 3, or Bombardment 3
"1 additional attack per turn."

Indirect Fire

Unit Types: Siege, Archery, Naval
"Ranged attacks may be performed over obstacles." Requires: Targeting 1, Bombardment 1, Accuracy 1, or Barrage 1.
Notes: Unit with ranged attack may bombard targets it cannot see (as long as other friendly units can see them). Indirect Fire appears to be both a promotion and an attribute.

Volley

Unit Types: Ranged
+25% Combat Strength vs. Fortified units. Requires Accuracy 1, or Barrage 1.

Cover 1-2

Unit Types: Melee, Ranged
Cover 1: +25% defense against all ranged attacks. Requires Shock 2, Drill 2, Accuracy 1 or Barrage 1.
Cover 2: +25% defense against all ranged attacks. Requires Cover 1.

Mobility 1-2

Unit Types: Trireme, Caravel, Battleship
Mobility 1: +1 Movement. Requires: Shock 3, Drill 3, Targeting 1, or Bombardment 1.
Mobility 2: +1 Movement. Requires Mobility 1.

Scouting 1-3

Unit Types: Scout
Scouting 1: +1 sight range.
Scouting 2: +1 movement rate. Requires Scouting 1.
Scouting 3: +1 sight range. Requires Scouting 2.

Sentry

Unit Types: Knight, Scout, Warrior, Trireme, Rifleman, Mechanized Infantry
"+1 Visibility Range." Requires Shock 1, Drill 1, Targeting 1, or Bombardment 1.

Targeting 1-3 (Naval)

Unit Types: Naval, Air
Targeting 1: +20% Combat Strength against Naval units. 
Targeting 2: +20% Combat Strength against Naval units. Requires Targeting 1.
Targeting 3: +20% Combat Strength against Naval units. Requires Targeting 2. 

Supply

Unit Types: Naval
"May heal damage Outside of Friendly Territory. 2 HP healed per turn." Requires: Targeting 2, or Bombardment 2.

(Evasion)

Unit Types: B-17
Reduces damage from interception by 50%. Requires Siege 2 or or Bombardment 2.

Ambush 1-2

Unit Types: Melee, Air
Ambush 1: +25% Combat Strength vs. Armored units. Requires Shock 2, Drill 2, Interception 1, Dogfighting 1, Siege 1, or Bombardment 1
Ambush 2: +25% Combat Strength vs. Armored units. Requires Ambush 1.

Repair

Unit will heal every turn even if it performs an action. Requires: Shock 3, or Drill 3.
Note: Hammer icon

Blitz

Unit may attack multiple times per turn. Requires: Shock 3, or Drill 3.
Note: Lightning Bolt

Charge

+25% Combat Strength vs. damaged units. Required Shock 2, or Drill 2.
Notes: Sword with +

(Listed in Civilopedia)

This is a master list from Civilopedia. Note that there are sometimes several versions of each promotion.

Melee Promotions
Ambush 1-2: Bonus against Armored units.
Blitz: Multiple attacks per turn.
Charge: +25% bonus vs. damaged units.
Cover 1-2: +25% defense against ranged attacks.
Drill 1-3: Bonus fighting in rough terrain.
Formation 1-2: +25% bonus against mounted units.
Shock 1-3: Bonus fighting in open terrain.
Siege: +25% vs. Cities.

Ranged Promotions
Accuracy 1-3: bonus vs. units in open terrain.
Barrage 1-3: bonus vs. units in rough terrain.
Bombardment 1-3: bonus vs. land units.
Logistics: 1 additional attack per turn.
Mobility: +1 Movement.
Range: +1 Range.
Volley: +25% vs. fortified units.

Naval Promotions
Amphibious: Eliminates penalty attacking from sea or across rivers. (Anchor icon)
Supply: May heal damage outside friendly territory.
Targeting 1-3: bonus against Naval units.

Healing Promotions
Air Repair: Unit will heal every turn, even if it performs an action.
Heal Instantly: forgo a promotion to heal the unit to full.
March: heal while moving
Repair: heal while moving.
Survivalism 1-3: +1 healing per turn outside borders

Scouting Promotions
Scouting 1-3: bonuses to visibility and movement.
Sentry: +1 visibility range.

Air Promotions
Ambush 1-2: +25% vs. armored units
Dogfighting 1-3: +25% bonus for Air Sweep
Evasion: reduces interception damage by 50%
Interception 1-3: +25% when intercepting
Logistics: +1 attack
Mobility 1-2: + movement (?)
Range: +1 range
Siege 1-3: bonus vs cities
Sortie: +1 interception chance per turn
Targeting 1-2: bonus vs naval units

Shared Promotions
Discipline: +15% combat bonus from adjacent friendly unit. (provided by Social Policy)
Embarkation: allows naval embarkation
Great Lighthouse: +1 movement, +1 sight range. (provided by Wonder)
Himeji Castle: +25% combat strength in friendly territory. (provided by Wonder)
Indirect Fire: May bombard targets the unit cannot see, if other friendly units can see it. 
Morale: +15% combat strength, given by Heroic Epic national wonder.
Nationalism: +25% combat strength in friendly territory. (provided by Social Policy)
Oligarchy: +20?% combat strength for military units fighting within the empire's borders. (provided by Social Policy)

Unit Attributes

Red and Yellow Triangles

Unit Types: All
These appear to be generic icons for beneficial (yellow) and harmful (red) unit attributes.

Silver Triangle

Unit Types: Submarine, Zero, Jet Fighter, Missile Cruiser, Minuteman, Destroyer, Mechanized Infantry
I think this may indicate a vision-oriented ability, such as the ability to detect Submarines or the Air Recon ability (listed below). This would explain why it is seen on so many American land units (due to Manifest Destiny, which provides +1 vision range).

Lightning Bolt

Unit Types: All
This appears to be an older placeholder graphic, probably for all attributes. It has not been seen in current screenshots.

(Listed in Civilopedia)

Master list of Unit Attributes from the in-game Civilopedia. Not all of these are actually used on units in the game.

1 Extra Movement
Air Recon: Everything within 6 tiles of aircraft's starting location is visible at the beginning of the turn.
Air Sweep: Can Air Sweep to clear intercepting units.
All Tiles Cost 1 More
Astronomy Needed: Cannot enter deep Ocean until Astronomy.
Bonus vs. Aircraft (100)
Bonus vs. Cities (10)
Bonus vs. Cities (30)
Bonus vs. Fighters
Bonus vs. Helicopters
Bonus vs. Mounted (100)
Bonus vs. Mounted (50)
Bonus vs. Submarines (100)
Bonus vs. Submarines (50)
Bonus vs. Tanks
Can Carry (1-4) Cargo
Can Enter Rival Territory
Can Move After Attacking
Can See Submarines
Cannot Enter Deep Ocean
Cannot Enter Forest or Jungle
Combat Bonus in Forest/Jungle (50)
Combat Bonus in Jungle only (50)
Combat Bonus in Open Terrain
Combat Bonus When Attacking (25)
Damaged Enemy Bonus: 50% combat bonus against damaged enemy.
Evasion (100)
Evasion (50)
Extra Sight (1-4)
Foreign Lands Bonus: 20% combat bonus outside friendly territory.
Great Generals I: Combat Likely to create Great Generals.
Great Generals II: Combat Very Likely to create Great Generals.
Heal if Destroy an Enemy: Heals all damage if kills a non-Barbarian unit.
Heals 2 Damage IF Kills a Unit
Heals at Double Rate
Hovering Unit: unit may pass over mountains.
Ignores Terrain Cost
Interception (100)
Interception (20)
Interception (40)
Interception (50)
Is Invisible (Submarine)
Leadership: Improves combat effectiveness of nearby units.
Limited Visibility: -1 visibility range.
May Attack Twice
May Enter Ice Tiles
May Not Melee Attack
May Paradrop
Must Set Up to Ranged Attack
Naval Movement: 2 extra movement for Naval units (English unique ability).
No Defensive Bonuses
No Movement Cost to Pillage
Penalty Attacking Cities: 40% penalty attacking cities.
Penalty on Defense
Penalty vs Mounted
Penalty vs Naval
Ranged Support Fire: Provides Support Fire to friendly units when fortified.
Rough Terrain Penalty: Entering Rough Terrain consumes all movement.
Unable to Capture Cities
Weak Ranged Attack: -50% Strength when using ranged attack.