The Ranger is the Light Unit of the Colonial Age. It is a well-balanced army unit, with very respectable attack and defense stats. They are most effective against fast units and ranged units. It has a huge leap in attack and defense compared to Great Sword Warrior, gaining +10 on defense and attack. It is very effective against all fast units and is useful for attacking artillery units. However, it should avoid heavy units.
Rangers are special as they are the first unit in the game to have the 'Stealth" ability. This allows them to be immune from ranged attacks IF they are standing in a forest. In order to attack a Ranger, a unit must be in a hex that is adjacent to it. This ability greatly makes ranged and artillery units much less effective against the Ranger. However, forests are not on every map in sufficient quantities, so don't expect to be counting on this ability too much.
Against Same Age Units
Rangers are very effective against the Dragoon. However, the Dragoon has much more defense than fast units before it, so the Ranger can be said to be less effective against the Dragoon than past light units against fast units. When hiding in forests and bushes, Rangers can take minimal damage against the Dragoon.
The Grenadier, the heavy unit and the counter to the Ranger, gains a ranged attack. This greatly reduces the Ranger's effectiveness against them, as Rangers will not be able to retaliate in case they are hit by a Grenadier. Taking advantage of the Stealth ability can nullify this, however, Rangers should still avoid combat with Grenadiers. Rangers should wait until the Grenadier is away from plains and into forests or bushes to attack them.
The Ranger gains an advantage against the Musketeer with the Stealth ability. Rangers hiding in forests will force Musketeers to get very close to attack, allowing Rangers to easily take them out. However, Musketeers now have 7 range, allowing them to do damage from a far distance. However, Rangers are able to kill a Musketeer in two hits, so all Rangers have to do is to get close the Musketeer, which isn't too hard, considering the average movement speed of the Musketeer.
The artillery unit of the age, the Field Gun, is very ineffective against the Ranger. Rangers can be used in substitute for the Dragoon for taking out Field Gun armies. Even if the Field Gun gets onto hills for an attack bonus, Rangers take only average damage. Players should note that the Field Gun has a massive range, able to hit Rangers even on the other side of the map.