The first known example of double-effect reasoning is Thomas Aquinas' treatment of homicidal self-defense, in his work Summa Theologica.
A tactical bomber engages in strikes on enemy military targets, knowing that some civilian casualties are a foreseen but unintended consequence.
While civilian casualties occur in both cases, the tactical bomber’s intention is not to cause harm, and the action itself is aimed at a legitimate military goal.
[6] Alyson Hoyt argues that the DDE should not be used in wartime due to its potential for misuse and the complexity of modern warfare.
She claims while the DDE aims to justify actions with unintended harmful consequences, it can be easily manipulated to rationalize civilian casualties as mere "side effects" of military objectives.