On Bhagavad Gita: Can an egoless one engage in a war?

The following is an excerpt from a samvaad (dialogue) session with Acharya Prashant.

यस्य नाहङ् कृतो भावो बुद्धिर्यस्य न लिप्यते ।।

हत्वाऽपि स इमाँल्लोकान्न हन्ति न निबध्यते ।। 18.17 ।।

yasya nāhankṛito bhāvo buddhir yasya na lipyate

hatvā ‘pi sa imāl lokān na hanti na nibadhyate

He who is free from the notion of egoism, whose intelligence is not affected by good or evil, though he kills these people, he kills not, nor is bound by the action.

~ Shrimad Bhagavad Gita, Chapter 18, Verse 17

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Questioner (Q): Please help me understand this. If one does not have the feeling of egoism, then how can he even perform the very act of killing or not killing? And if does act, for whom does he perform that action?

Acharya Prashant (AP): The question is based on an assumption. What does the question say? “If someone does not have egoism, how can he perform the act of killing or not killing?” Now, take killing and not killing together, and you have the universal set of all actions that can be performed by anybody ever, right? You have the set A, and then you add to it A complement, and what do you get? The universal set. Take any person ever, and you can categorize his actions in one of these two categories: he is either killing, or not killing. Right?

What is the questioner saying? “If one does not have the feeling of egoism, then how can he perform the very act of killing or not killing?” In other words, what he is saying is, if one does not have egoism, then how can he act at all? Because killing and not killing together is the universal set of all actions. So, the questioner is saying, “If one does not have egoism, how can he perform any action?” Right? That’s the question. The question is: If one does not have egoism, how can he perform any action? A or A complement — he can do nothing. That’s the assumption behind the question.