Alexander became king of Macedonia in October 336, but he was not the only candidate. One of the rivals, a man named Attalus, was put to death by Parmenion, the most important general of Alexander's father Philip II. This was remarkable, because Parmenion was related to Attalus. Alexander owed something to the old general and was forced to do something in return, especially since Parmenion commanded a big army, the vanguard of an expeditionary that the Macedonians had sent against the Achaemenid empire.
Alexander knew what he was expected to do, and in the next years, we find many relatives of Parmenion in key positions in the Macedonian army. For example, his youngest son Nicanor became commander of the infantry regiment that was known as the Shield bearers, his son-in-law Coenus commanded a phalanx battalion, and another Nicanor was admiral of the navy of the Greek allies. Parmenion's friend Amyntas and his brother Asander received other honorable positions. Parmenion himself was Alexander's second in command.
The most important appointment, however, was that of his oldest son Philotas: he was the commander of the Companion cavalry, a unit of eight squadrons (of 225 horsemen each) that was Macedonia's most effective weapon in any battle. Until then, Philotas had only commanded a cavalry squadron from Upper Macedonia.
In his new position, Philotas was present at all great battles of Alexander's Persian campaign. Together with his king, he led the cavalry charge at the Granicus river (June 334), he prevented the Persian navy from finding a safe anchorage during the siege of Miletus (Summer 334), and was present at the beginning of the siege of Halicarnassus. During the winter, the Companion cavalry was part of Parmenion's army group, which moved from Sardes to the east along the Royal road, occupying Gordium in the winter.
During the great battle of Issus, Alexander successfully used the Companions as a crowbar to create a gap in the Persian lines (November 333) and during the siege of Tyre, he again used Philotas' men during the main charge (July 332). No activities of the regiment are mentioned during the second half of the year, but it is certain that at least one unit was with Alexander when he subdued Egypt. As we will see below, Philotas was also in Egypt. However, he is not mentioned in the accounts of Alexander's famous visit to the oracle of Ammon at Siwa.
The decisive battle in the war against Persia took place on 1 October 331, at Gaugamela in the north of Mesopotamia. Again, Alexander used the Companion cavalry as a crowbar and again, he was victorious over the Persians (who were demoralized after evil omens). In the last weeks of the year, the Companions were present during the battle at the Persian gate, and in the spring of 330, Alexander used them to pursue the last Achaemenid king of Persia, Darius III Codomannus. When he had been killed, half of Philotas' regiment went to western Hyrcania; it is not clear whether their commander was with them.
Passing through Parthia and Aria, the Macedonians reached Drangiana. By now, many soldiers were discontent. They had been expecting to return home after the fall of the Achaemenid empire and the death of its king. However, they were now forced to march to the east and nobody knew what their king was doing. Moreover, it seemed that Alexander was more and more becoming something of a Persian king himself, something the soldiers did not appreciate. Officers of the old school like Parmenion were sent on honorable missions - but were conspicuously far away from the royal court. These were clear signals that the war was to continue for a long time.
In December 330, Philotas was accused. He was said to have known of an earlier conspiracy by ordinary Macedonian soldiers who wanted to kill their king, and not to have reported it. This was not the first time that Philotas was accused: something similar had already been brought to Alexander's attention when he was in Egypt. Back then, Alexander had ignored the rumors. This time, however, there was solid evidence that soldiers had attempted to kill the king, and the accusations against Philotas were taken seriously.
At first, Alexander forgave Philotas, but the next day, the accusations were renewed by the phalanx commanders Craterus and Coenus, Philotas' brother-in-law. It is not known whether they had a secret agenda, but we may be suspicious, now that we see two infantry commanders accusing the leading cavalry commander. During the night, Philotas was arrested. According to Quintus Curtius Rufus, Philotas only said to the king that the bitter hatred of his enemies had triumphed over Alexander's kindness.
As the army exercised capital jurisdiction in Macedonia, Alexander organized a trial. He accused Philotas and produced an intercepted letter from Parmenion to his son that contained the line "first of all take care of yourselves and the of your people - that is how we shall accomplish our purpose". This was no real evidence, but the court found Philotas guilty of conspiracy.
However, the precise nature of the conspiracy was still unknown. Hephaestion, Craterus and Coenus declared that torture should be employed to force the truth out of Philotas. He confessed that he and his father had wanted to kill Alexander, whose claim to be a god was scandalous. The plan had been postponed until Darius was dead, because otherwise, the enemy would benefit from it, whereas with the Persian leader removed, Asia and Europe would be the reward of the assassination. The soldiers' conspiracy had offered an excellent opportunity. Having confessed all this, Philotas and a few others were speared or stoned to death. To commemorate the event, Alexander renamed the city where the conspiracies had been detected Prophthasia or Anticipation (modern Farâh).
It is not clear what really happened. No ancient author doubts that the first conspiracy was a fact; the problem is the conspiracy of Philotas and Parmenion. The confession of the tortured man can, of course, not be taken as proof that he and his father were really attempting to gain the kingdom. On the other hand, it is strange that Philotas did not report the first conspiracy. It is possible that he wanted to see what happened: if the soldiers' attempt failed, nothing was lost, if it were successful, the army would chose him as its commander and king. But although he had much to gain, the fact that he had a motive does not mean that he really did what he was accused of. We will never known what really happened.
The consequences of the murder were clear. In the first place, from now on, the Companion cavalry had two commanders, Clitus and Hephaestion. This was a safety measure against too powerful commanders.
In the second place, the execution of Philotas made the murder of his father Parmenion inevitable. Whether the son had been guilty or not was unimportant: the father was too powerful to stay alive. He was in Ecbatana, where he controlled the road from the Mediterranean to the East, large sums of money and many troops, reinforcements that were delayed. Therefore, Alexander sent an express messenger, whose duty it was to be at Ecbatana before the news of the death of Philotas reached Parmenion. The courier gave letters to the commanders of the reinforcements, and they killed the old general.
Sabine Müller, Maßnamen der Herrschaftssicherung gegenüber der makedonischen Opposition bei Alexander dem Großen, 2003 Frankfurt am Main.