Morse's assessment of siege warfare and his feelings of regret were common in Union camps in 1864. On the one hand, cities played a central role in both Union and Confederate military strategies. It was not enough to have the strongest or largest army in the field; one must take the enemy's centers of production and politics as well. And under the established laws of warfare, cities were legitimate military targets.

On the other hand, the presence of noncombatants within them complicated the moral calculus of bombardment. In the discussions about "civilized warfare" that circulated during the Civil War, engaging in acts of destruction hurtful to "women, children, sick, wounded, and aged" was disreputable at best and the work of what Southerners called "the Vandal horde" at worst. Morse vacillated on this issue but ultimately embraced the most common defense of siege and hard war tactics: military necessity.

Morse agreed with Sherman - whom he judged "the most original character and greatest genius there is in this country" - that the citizens of Atlanta had brought destruction upon themselves. Even though the shelling of the city seemed "almost inhuman," Morse concluded that it was simply "one of the horrors of war."