Luck was definitely involved. In chaotic situations, such as a battlefield anything can happen. As an example here's a record[0] of Alexander almost dying:

    At Granicus, Alexander was hit in the head by scimitar-wielding cavalry, causing his helmet to fly off his head. The Persians later struck the king with a missile, which went through his shield and lodged in his shoulder.

- The head hot could have given him a serious concussion, even causing him to fall unconcious making his troops think he died and plummeting morale. - The arrow could have pierced his heart instead of his shoulder after going through his shield.

The real point is that such an accomplishment will never be due to pure luck. Skill also had to be there.

[0]: https://www.military.com/history/alexander-great-caught-luck...