View source for 222 BC

=== By place ===

==== Roman Republic ====
* The [[Roman Republic|Roman]] [[consul|consuls]] [[Marcus Claudius Marcellus]] and [[Gnaeus Cornelius Scipio Calvus]] march into [[Insubres]] territory and besiege [[Acerrae (Cisalpine Gaul)|Acerrae]], an Insubre fortification on the right bank of the River [[Adda River, Italy|Adda]] between [[Cremona]] and [[Laus Pompeia]]. The Insubres are unable to relieve Acerrae because the Romans control all the strategic points around it. Therefore, they hire 30,000 [[Gaesatae]] mercenaries, led by [[Viridomarus]] (or Britomartus), who march to [[Clastidium]], an important and strategically situated town, owned by the [[Marici (tribe)|Marici]], a [[Ligures|Ligurian]] tribe allied to the Romans, they start a siege hoping that this will force the Romans to lift their siege of Acerrae to come to Clastidium's aid.<ref>[[Polybius]], The Histories, 2.19-20</ref>
*The Romans split their forces. [[Marcus Claudius Marcellus]] heads for [[Clastidium]] while his colleague [[Gnaeus Cornelius Scipio Calvus]] continues the siege of [[Acerrae (Cisalpine Gaul)|Acerrae]]. At the [[Battle of Clastidium]] Marcellus defeats the [[Gaesatae]]. Marcellus personally slays [[Viridomarus]]. This victory removes the Gallic threat to Rome. Marcellus is awarded the [[spolia opima]] for the third and last time in Roman history.<ref>[[Polybius]], The Histories, 2.19; [[Plutarch]], ''Marcellus'', 6-7.</ref>
* After taking Acerrae [[Gnaeus Cornelius Scipio Calvus]] marches on [[Mediolanum]] (modern [[Milan]]), another [[fortification|stronghold]] of the [[Insubres]], which also falls into [[Roman Republic|Roman]] hands, upon which the chieftains of the Insubres lose all hope and [[Unconditional surrender|surrendered unconditionally]].  Thus the Romans succeeded in conquering the largest independent Celtic tribe in Italy and firmly established their hegemony over the [[Po Valley]], then the most productive agricultural region in the peninsula.<ref>[[Polybius]], The Histories, II 17,4-5 and 20.</ref>

==== Greece ====
*[[Battle of Sellasia]]: [[Cleomenes III]] of [[Sparta]] is defeated by [[Antigonus III Doson|Antigonus III]] of [[Macedonia (ancient kingdom)|Macedon]] and his allies (the [[Achaean League]], the [[Boeotian League]], the [[Acarnanians]], [[Epirus]] and the [[Illyrians]] under the command of [[Demetrius of Pharos]]) near [[Sellasia]] (north of Sparta) and flees to [[Ancient Egypt|Egypt]] under the protection of King [[Ptolemy III Euergetes|Ptolemy III]]. Antigonus III's forces occupy Sparta, which is the first time this city has ever been occupied.
* Almost all of [[Ancient Greece|Greece]] falls under [[Macedon]]ian [[suzerainty]] after Antigonus III re-establishes the Hellenic Alliance as a confederacy of leagues, with himself as president.

==== Seleucid Empire ====
* [[Seleucid]] forces under their general [[Achaeus (general)|Achaeus]] succeed in winning back all the Seleucid domains in [[Anatolia|Asia Minor]] (lost six years earlier to [[Pergamum]]).
* [[Mithridates II of Pontus]] gives his daughter [[Laodice III of Syria|Laodice]] in marriage to the Seleucid king [[Antiochus III the Great|Antiochus III]]. Another of his daughters, also named [[Laodice of Pontus|Laodice]], is married about the same time to general [[Achaeus (general)|Achaeus]].

==== China ====
* The [[Qin (state)|Qin]] general [[Wang Jian (Qin)|Wang Jian]] conquers [[Wu (region)|Wuyue]], forcing the capitulation of its ruler. The conquered region becomes the province of Kuaiji. This campaign completes the subjugation of the lands formerly held by the [[State of Chu]], and it also serves as a precursor for the [[Qin campaign against the Yue tribes]].
* The Qin generals [[Wang Ben]] and [[Li Xin (Qin)|Li Xin]] conquer [[Liaodong]], thereby completing the subjugation of [[state of Yan|Yan]].
* Wang Ben conquers [[Prince of Dai|Dai]], thereby completing the subjugation of [[state of Zhao|Zhao]].<ref>{{cite book|first=Sima|last= Qian|title=Records of the Grand Historian, Section: The First Emperor, Section: Wang Jian.}}</ref>
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