“Stronger than Onager. Wheeled siege weapon used to attack a small mass of units.”—Age of Empires II description
The Siege Onager is a ranged siege unit in Age of Empires II that can be trained at the Siege Workshop once the Imperial Age is reached. It is primarily used against large groups of enemies. Its high attack and splash damage make it a powerful unit, especially against archers and slow-moving units. Its main offsets are its low movement and projectile speed, minimum range, high cost, and tendency to harm friendly units caught in its blast. Siege Onagers can attack ground and cut down trees.
The * indicates that the civilization can fully upgrade their Siege Onagers, i.e. gets Siege Engineers. Faith and Heresy are not taken into account because they only contribute to their combat strength in a very situational manner.
Siege Onagers are arguably the most powerful siege weapon when it comes to killing other units. They are devastating against archers and slow-moving units, but cannot defend themselves against most melee units. Therefore, they need to be guarded in most situations. Archers are often used, because own melee units are usually endangered by the own Siege Onagers. But archers don't cover the Siege Onager's main weakness adequately, which is cavalry. Therefore, Siege Onagers are also often paired with Halberdiers. That combination is especially prominent with the Celts, Ethiopians, Koreans, and Slavs.
As Siege Onager is one of the most expensive upgrades in the game (but also one of the most powerful), the player has to carefully weigh whether it is worth it in a 1v1 game, but it can definitely turn the tide of a game with a few good shots in the right situation. Compared to the Onager, the Siege Onager has more health, damage, and pierce armor, but perhaps more importantly has a larger blast radius, making shots harder to dodge and able to hit more targets.
Upgrading to Siege Onager helps even out the playing field against one of the Mangonel-line's main weakness, the Bombard Cannon, to some extent. The reason for this is that the Siege Onager can take two Bombard Cannonballs, but can kill a Bombard Cannon in one full shot, while for the standard Onager it is the other way around. The large drawback of the much shorter range compared to the Bombard Cannon still remains however, so considering equal micromanagement skills and numbers, the Bombard Cannons should still come out on top. Another point to consider is invested resources: While the initial Siege Onager upgrade is very expensive, Bombard Cannons only require Chemistry (which is also useful for other ranged units), but Siege Onagers themselves are cheaper than Bombard Cannons, so in small numbers the Bombard Cannon is cheaper, but the higher the production numbers go, the more it evens out, until the cost of the Bombard Cannons actually surpasses the cost of Siege Onagers.
Further statistics Edit
|Unit strengths and weaknesses|
|Strong vs.||Buildings, Villagers, archers, units in dense formations|
|Weak vs.||Melee units especially Magyar Huszars and other melee cavalry, Mangudai, Woad Raiders, Condottieri, Bombard Cannons, Eagle Warriors|
|Hit points||Furor Celtica (+40%, Celts only)|
|Attack|| Siege Engineers (+20% attack against buildings)|
Torsion Engines (increases blast damage radius, Ethiopians only)
|Range|| Siege Engineers (+1)|
Shinkichon (+1, Koreans only)
|Armor||Ironclad (+4/+0, Teutons only)|
|Movement Speed||Drill (+50%, Mongols only)|
|Conversion defense|| Faith|
Civilization bonuses Edit
- Aztecs: Siege Onagers are created 18% faster.
- Celts: Siege Onagers fire 25% faster. Siege Onagers can convert herdables even if enemy units are next to them.
- Slavs: Siege Onagers are 15% cheaper.
Team bonuses Edit
- A team containing Celts: Siege Onagers are created 20% faster.
- A team containing Koreans: Siege Onagers minimum range reduced.
- A team containing Malians: Researching Chemistry and Siege Engineers is 80% faster.
- A team containing Teutons: Siege Onagers are more resistant to conversion.
- A team containing Lithuanians: Researching Heresy and Faith is 20% faster.
The Age of Kings Edit
- Onagers move at a speed of 0.5.
- Researching Chemistry reduces the projectile speed from 3.5 to 2.9.
The Conquerors Edit
- Siege Onagers now move at a speed of 0.6.
- Siege Onagers gain +12 bonus damage against siege weapons.
- Heresy introduced.
- Celts: Furor Celtica introduced. It gives Siege Onagers +50% HP.
- Mongols: Drill introduced.
- Koreans: Shinkichon initially gives Siege Onagers +2 range. With patch 1.0c, the effect was reduced to +1.
- A team containing Koreans: Siege Onagers have +1 range.
The Forgotten Edit
- Researching Chemistry does not affect the projectile speed anymore.
- Celts: Furor Celtica now gives +40% HP to Siege Onagers.
- Teutons: Ironclad introduced.
- A team containing Koreans: Siege Onagers minimum range reduced by 2 (instead of +1 range).
- The total cost to upgrade Mangonels to Siege Onagers is 2,250 food and 1,500 gold, making Mangonels the most expensive units to upgrade.
- Despite the description given in the manual for the Siege Onager, it does not have any additional range over the Onager.
- Before The African Kingdoms was released, the Siege Onager was the most exclusive unit in the game, i.e. no other unit was available to fewer different civilizations. With the introduction of The African Kingdoms, however, that title was lost to the Paladin. With the release of the Definitive Edition, however, the Siege Onager is tied with the Paladin as the most exclusive unit in the game.
“The siege onager was the largest upgrade of the onager line of weapons. It had the longest range and did the most damage.”
In the Ancient Roman Empire, Onagers were designed to be used against lightly fortified towns, and massive armies, and thus the upgrade of this, armed the Onager with metal plates, were built twice the size and could fire medium and even large boulders to weaken walls that rams were not able to access. However, the Byzantines do not have access to the Siege Onager, despite being the Roman Empire's continuation.
In Medieval Times, Mangonels and Trebuchets were used in sieges as they proved to be more useful against large fortified walls.