Alexander the Great ascends to the Macedonian throne at age 20 following the assassination of his father Philip II at Aegae, marking the beginning of one of history's most significant reigns.

Alexander the Great's ascension to the Macedonian throne marked a pivotal moment in ancient history. At just 20 years old he inherited not only a kingdom but also his father's vision of conquest and expansion. The year was 336 BCE when the assassination of his father Philip II thrust the young prince into power.

The circumstances surrounding Alexander's rise to kingship were as dramatic as his later conquests. His father's murder at the wedding feast of Alexander's sister Cleopatra created a power vacuum that required swift action. Despite his youth Alexander quickly consolidated his authority demonstrating the leadership skills that would later help him build one of history's largest empires.

Alexander ascended to the Macedonian throne following the dramatic assassination of Philip II during a public celebration. The sudden transition marked the beginning of a new era in Macedonian history as the 20-year-old prince became king.

Philip II's assassination occurred at the wedding celebration of his daughter Cleopatra to Alexander I of Epirus in October 336 BCE. A royal bodyguard named Pausanias stabbed Philip in the theater at Aegae, the ancient capital of Macedonia. Historical accounts from Diodorus Siculus reveal that Pausanias acted in revenge for personal grievances against the king.

Event Details	Description
Date	October 336 BCE
Location	Theater at Aegae
Assassin	Pausanias (Royal Bodyguard)
Occasion	Royal Wedding Celebration

Alexander secured his position as the rightful heir through swift political maneuvering. He eliminated potential rivals including his cousin Amyntas IV who held a competing claim to the Macedonian throne. The army supported Alexander's succession, recognizing his military training under Philip II's leadership. The Assembly of the Macedonian Army formally proclaimed him king, giving him the title Alexander III of Macedon.

Key Actions	Timeline
Army Recognition	Immediate
Assembly Proclamation	Within days of Philip's death
Rival Elimination	First month of reign
Consolidation of Power	Late 336 BCE

After ascending to the Macedonian throne, Alexander faced immediate threats to his authority from both internal opposition and neighboring territories seeking to exploit the transition of power.

Alexander swiftly eliminated potential rivals to secure his position as king. He ordered the execution of key conspirators linked to his father's assassination including members of the Lyncestian house. The young king also neutralized threats from potential claimants to the throne such as his cousin Amyntas IV. Several Greek cities including Thebes Athens challenged Macedonian rule following Philip II's death but Alexander's rapid military response crushed these revolts demonstrating his tactical prowess.

Alexander launched decisive campaigns against rebellious northern tribes in 335 BCE. He led military expeditions against the Thracians Triballians subjugating these territories through a series of swift victories. The campaign extended to the Danube River where he defeated the Getae tribes. In the west Alexander subdued the Illyrians who attempted to break away from Macedonian control establishing firm control over Macedonia's frontier regions. These victories secured the northern borders of the Macedonian Empire preventing future invasions from tribal forces.

Campaign	Year BCE	Outcome
Thracian-Triballi	335	Complete subjugation
Getae	335	Macedonian victory
Illyrian	335	Restoration of control

Alexander's military education began at an early age under the direct supervision of his father, Philip II, who transformed Macedonia into a formidable military power. His comprehensive training laid the foundation for his future conquests and military innovations.

Philip II introduced Alexander to advanced military tactics from age 12. Alexander participated in cavalry drills, weapons training, and strategic planning sessions with Macedonian generals. By age 16, he commanded a portion of the Macedonian army at the Battle of Chaeronea in 338 BCE, leading the decisive cavalry charge that secured victory.

Military training components included:

• Combat techniques with the Macedonian long spear (sarissa)
• Horseback riding and cavalry maneuvers
• Battle formation strategies
• Siege warfare tactics
• Leadership of military units

Aristotle taught Alexander from 343-340 BCE, complementing his military education with intellectual training. The philosopher's teachings enhanced Alexander's strategic thinking through:

Key areas of study:

• Military strategy through historical analysis
• Geography and natural sciences for campaign planning
• Politics and governance principles
• Greek literature focusing on military epics
• Logic and reasoning for tactical decision-making

Training achievements:

Year	Military Milestone
340 BCE	First military command
338 BCE	Victory at Chaeronea
336 BCE	Army commander status

This military and intellectual foundation proved essential when Alexander assumed the Macedonian throne, enabling him to immediately assert authority over the army and expand the empire his father built.

Alexander's initial actions as king focused on establishing control over the Macedonian Empire through strategic military campaigns. His swift response to challenges solidified his authority across Greece within his first year of rule.

Alexander launched decisive military campaigns to maintain Greek territories under Macedonian control. He crushed a Theban rebellion in 335 BCE by destroying their city, leaving only the temples intact. This demonstration of power prompted Athens to abandon its resistance, reaffirming the League of Corinth's loyalty to Macedonian rule. The Greek cities renewed their allegiance to Alexander, accepting him as the successor to his father's position as hegemon of the Hellenic League.

Alexander reorganized the Macedonian military structure inherited from Philip II to prepare for eastern expansion. He appointed experienced generals like Parmenion to key positions, strengthened the army's logistics, and assembled a force of 43,000 infantry and 6,000 cavalry. The army incorporated:

• Advanced siege weapons engineered specifically for Persian campaigns
• Specialized units trained in mountain warfare tactics
• Mixed Greek-Macedonian cavalry formations
• Supply networks extending across conquered territories

Military Component	Number of Troops
Infantry	43,000
Cavalry	6,000
Support Personnel	7,000
Naval Forces	120 ships

Alexander secured the northern borders through treaties with neighboring tribes, established supply routes through Asia Minor, and gathered intelligence about Persian defenses. He stationed garrison forces in key Greek cities to maintain control during his planned eastern campaign.

Alexander's initial military campaigns as king demonstrated his exceptional tactical abilities inherited from his father Philip II. His swift response to challenges across the Greek territories established his authority as the new ruler of the Macedonian Empire.

Alexander confronted his first major military challenge when Thebes revolted in 335 BCE. He mobilized the Macedonian army with unprecedented speed, covering 240 miles in 13 days. The siege lasted 3 days, resulting in the complete destruction of Thebes. Alexander ordered:

• Demolition of 6,000 buildings

• Execution of 6,000 Theban soldiers

• Sale of 30,000 survivors into slavery

• Preservation of only temples religious structures

• Accepting Athens' formal apology without retribution

• Maintaining the Corinthian League structure established by Philip II

• Appointing loyal governors in key Greek territories

• Establishing military garrisons at strategic points

• Implementing diplomatic measures through the Hellenic League

Military Action	Year BCE	Result
Siege of Thebes	335	City destroyed, rebellion crushed
Athens Submission	335	Diplomatic settlement achieved
Northern Campaign	335	Tribal territories secured
Greek Unification	334	Complete control established

• Alexander the Great became King of Macedon in October 336 BCE at the age of 20, following the assassination of his father Philip II at a wedding celebration in Aegae.
• The transition of power was swift, with Alexander quickly securing support from the Macedonian Army and receiving formal proclamation from the Assembly within days of Philip's death.
• Alexander faced immediate challenges after becoming king, including internal opposition and threats from neighboring territories, which he effectively crushed through military campaigns.
• His early military training under Philip II and education from Aristotle (343-340 BCE) prepared him well for leadership, having already commanded troops at the Battle of Chaeronea in 338 BCE.
• Within his first year as king, Alexander demonstrated his military prowess by destroying Thebes in 335 BCE, securing Greek territories, and preparing for his future Persian conquest with an army of 43,000 infantry and 6,000 cavalry.

Alexander the Great's ascension to the Macedonian throne at age 20 marked the beginning of one of history's most remarkable military careers. His swift actions to secure power demonstrated the leadership qualities that would define his reign. Through strategic military campaigns eliminating internal threats and swiftly crushing external rebellions he established unquestionable authority over the kingdom.

The young king's comprehensive military training and education under both his father Philip II and Aristotle prepared him perfectly for leadership. These foundations combined with his natural tactical brilliance enabled him to transform from prince to king to legendary conqueror. His early years as king set the stage for the unprecedented military campaigns that would create one of the ancient world's largest empires.