Which of Alexander's generals wrote a history of his campaigns that later became a key source? Ptolemy I Soter wrote a history of Alexander’s campaigns that later became an important source. Ptolemy had served alongside Alexander as a trusted officer and one of his bodyguards, participating in campaigns from the conquest of Persia through Afghanistan and India.
After Alexander’s death in 323 BCE, Ptolemy established himself as satrap and later king of Egypt. He wrote his history from the perspective of a senior commander and eyewitness, although the original work is now lost. Much of its content is believed to survive indirectly through later authors, especially Arrian in the Anabasis of Alexander.
Arrian regarded Ptolemy as particularly valuable because he had personally witnessed many events and held royal status, which Arrian thought gave him a reason to avoid dishonest exaggeration. Modern historians still treat the tradition cautiously: Ptolemy had political reasons to present Alexander, himself, and the Macedonian leadership favorably. The answer is not Perdiccas, Nearchus, or Seleucus; those men had important military roles, but Ptolemy is the general specifically associated with a surviving influence on Alexander’s historical tradition.