Command in ancient armies was a collective as much as an individual endeavour, because the primitive communications made it hard for one man to exercise control even over the relatively short distances involved. Indeed, command limitations seem to have been a major reason why large armies formed up in greater depth, rather than trying to coordinate operations across an unpractically long front. Pre-planning and delegation of authority to local subordinates were the norm, and some forces did not even have a single overall general. It was because command was so problematic that most ancient armies achieved so much less than the troops themselves were theoretically capable of, as inertia and confusion reduced movement rates and inhibited decisive attacks. This meant that asymmetries in command, which allowed one army to suffer less than its opponents from the restrictions involved, could have a major impact on fighting performance.
Perhaps paradoxically, given the difficulties for any single individual of maintaining real-time control of anything more than a small segment of the battle line, this was the golden age of ‘great captains’ like Alexander, Hannibal, Scipio and Caesar whose generalship was a very significant determinant of victory. The explanation seems to be that there were many other ways in which such individuals contributed to success besides their personal influence during the battle itself. Training and motivating their troops and building up capable subordinates in the months and years beforehand could significantly improve the quality of the army as a whole. Winning the intelligence contest could allow novel pre-planned deployments and manoeuvres precisely tailored to counter the enemy battle line, and seizing the initiative could panic or provoke the enemy into hurried reactions that left their army vulnerable and unprepared. The actual fighting was thus only the culmination of an overall process that stacked the odds heavily in favour of the better-commanded side.