In 356 B.C., Alexander was born into a state
that was already in the midst of  great change. His father, Philip
II, who was largely responsible for these  changes, had given Alexander
a united Hellenic League over which to rule. As  Macedonia had hitherto
been looked upon as semi-barbaric, when Philip  reorganized the
state and conquered Athens and Thebes, the rest of the Greek  city-states
were reluctant to submit themselves to Macedonian rule. Indeed,
 though they would succeed in keeping Greece in line, neither Philip
nor  Alexander ever had the sincere loyalty of his citizens, for
Greece could never  get past its resentment of Macedonia. Moreover,
it did not help the ruler's  cause that republicanism–and even democracy–were
being explored in  the individual city-states. Aristotle must have
had a difficult time educating  the young prince Alexander to become
a monarch when he likely doubted the  justice of that position.
Alexander also inherited the legacy of the Persian invasion.
His father had long  dreamed of the idea of invading Persia but
had died before he could achieve it.  The roots of the conquest
were manifold. Formally, it was carried out to free  Greek cities
under the rule of Persia and to revenge wrongs done to Greece in
 the past. Money may also have been a factor, as Alexander was in
significant  debt and counted on tapping into the opulence of Persia.
Perhaps more important,  the prevailing sentiment of the times was
that non-Greeks were barbarians and  deserved to be enslaved. Even
the enlightened Aristotle was adamant in this  belief, and he educated Alexander
to that extent. Alexander himself would depart  from his former
master, and his desire to cooperate with Persians earned him the
 resentment of many conservative Macedonians.
Alexander's opposition, then, stemmed from two corners–the Greek
city-states, which were constantly looking for a chance to rebel
against him, and his  own Macedonians, who objected to his attitude
toward the Persians. The  differences between Persia and Greece
were significant in practice as well as  theory, which led to many
conflicts in the court. Alexander, for his part, made  many concessions
and adaptations to the Persian way of life, including  participation
in religious rituals and marriage Persian women–which served  only
to worsen his unpopularity.
Conquest was Alexander's main–and perhaps only–ambition. He
was  fortunate that the power of Persia was in decline. He of course
preceded the  Roman Empire, but the idea of building such an empire
was far from new. Most  territories were used to the fact of outside
rule; some fought and others  conceded. It is significant, however,
that each territory had to be dealt with  individually, for defeating
the Great King was not sufficient in itself.
The construction of Alexander's life is itself problematic,
for it is difficult  to separate fact from legend. In general, historians
have had to deduce the  truth by evaluating a variety of sources
and stories. When uncertainties  persist, more than one account
must be acknowledged. One of the most famous  sources is Plutarch's Lives.