Why do you think he calls the act a military necessity in the last section?

He likely labels the act a military necessity to justify actions that may be seen as extreme or controversial, framing them as essential for the success of a military campaign or the protection of national interests. By using this term, he aims to convey that the choices made were not taken lightly, but rather were deemed crucial for achieving a strategic objective. This rationale can also serve to rally support or understanding among those who might question the morality of the actions taken. Ultimately, it reflects a pragmatic approach to decision-making in the context of warfare.