The Supply Wagon is an unarmed unit used to support troops outside of their nation's borders. It protects units from taking attrition damage and decreases the reloading times of nearby siege and artillery units. The Supply Wagon becomes available at the Siege Factory once a nation has entered the Medieval Age.
Units moving or fighting in enemy territory without a Supply Wagon nearby often suffer from attrition damage (red glow under the unit) and eventually might even die of it. Note, that the strength of attrition damage may vary, depending on age, Attrition technologies (researched at a Tower), Wonders and nation. Also, a few units, including the Supply Wagon itself, are immune to attrition damage under normal circumstances.
Siege and artillery units outside their own nation's borders are considered 'out of supply', when not within the range of a Supply Wagon. They reload and fire at a much slower rate, with early ages siege units (Catapults and Trebuchets) reloading at 66% of normal speed and artillery units from the Gunpowder Age on reloading at 50% of normal speed.
When an artillery unit is selected, a small icon in the status bar indicates, if it's "in supply" or "out of supply".
Supply Wagons counter these two negative effects, thus are especially indispensable for assaults on cities and other long term military operations in enemy territory. However, Supply Wagons are somewhat expensive due to their high ramping cost (see below) and bringing two or three Supply Wagons with every army is usually more than sufficient. Also note that a Supply Wagon can only supply units of its own nation – not allied units.
Destroying a Supply Wagon yields a one-time bonus of 50 Wealth.
Healing effect[]
The Versailles wonder adds a healing effect to Supply Wagons, allowing them to slowly heal/repair units within their range. Only land units of the same nation are affected; ships, aircraft, buildings and allied troops all are excluded from the effect. Also, a Supply Wagon cannot heal itself or other Supply Wagons – they still have to be garrisoned inside a city, Fort or Siege Factory/Factory in order to be repaired.
Healing occurs at a rate of one hit point per 1.33 seconds and a green glow appears beneath receiving units every time a hit point is healed (similar to the 'red attrition glow'). The effects of two or more Supply Wagons do not stack. The healing rate is fairly low – fully restoring the hit points of early ages infantry or cavalry might take up to four minutes. However, the effect is usually strong enough to heal most damage done by minor raiding parties, artillery weapons, towers and cities.
French Supply Wagons have an innate ability to heal nearby units at a rate of one hit point per 1.33 seconds. Owning the Versailles wonder doubles the healing rate to one hit point healed per 0.66 seconds, which essentially halves the total healing time of units.
Upgrading and unit costs[]
Supply Wagons cannot be upgraded directly, but some of their stats can be improved by researching Forage, Supply and Logistics at the Smelter. Each upgrade increases the Supply Wagon's hit points (+20 per upgrade), range (+2 per upgrade) and movement speed (roughly +15% per upgrade).
When a nation enters the Industrial Age, all of its Supply Wagons automatically become more modern cargo trucks (somewhat resembling the M35 cargo truck). The unit's stats, however, remain unaffected from this upgrade.
Supply Wagon's production cost increases progressively for every other Supply Wagons, whether on the field or currently in production, by a fixed 40 Food and 40 Timber, which is capped at 240 Food and 240 Timber.
Nation powers[]
The FrenchPower of Leadership: In addition to the healing effect mentioned above, receive a free Supply Wagon with every Siege Factory built, even before Medieval Age. However, they still have to advance to Medieval Age before being allowed to create additional ones at the factory.
The RussianPower of the Motherland: Cavalry units get an additional 25% damage bonus when attacking enemy Supply Wagons.
Unique units[]
The Dutch build Armed Supply Wagons instead, which is equipped with a light weapon to provide basic defense against raiding attacks.
Trivia[]
The unique Supply Wagons of the Gunpowder Age, used by the Indians and Persians, the Iroquois and Lakota, and the Americans.
In the original Rise of Nations, all Supply Wagons used the same pre-Industrial Age wagon models. But those wagons have unique models for the nations introduced in the Thrones and Patriots expansion (except for the Dutch). Some notable details about the unique models:
attrition damage and decreases the reloading times of nearby siege and artillery units. The Supply Wagon becomes available at the Siege Factory once a nation has entered the 
Medieval Age.
Gunpowder Age on reloading at 50% of normal speed.
Wealth.
Industrial Age, all of its Supply Wagons automatically become more modern cargo trucks (somewhat resembling the M35 cargo truck). The unit's stats, however, remain unaffected from this upgrade.
Food and 40 
Timber, which is capped at 240 
Medieval Age. However, they still have to advance to 
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