There are a number of legal issues that soldiers must consider whenever they use force—a subject I explored in some depth for “The Kill Company,” a story about a war crime that I wrote for The New Yorker last year. (Subscribers can read the full text; others can buy access to the issue.) Here are a few quick legal and command-culture issues that came to mind while I was watching the (http://collateralmurder.com/) and released on WikiLeaks today:

Proportionality. A longstanding feature of the Law of Armed Conflict, which has been incorporated into the Army’s Rules of Engagement, is the concept of proportionality: all military action must be necessary and proportional to a given threat. This means that soldiers cannot legally shoot down a couple of young teenagers who are throwing stones at a tank. It also requires that soldiers judge, sometimes under difficult circumstances, the advantages of an operation against the potential collateral damage. (The advantages must outweigh the estimated loss of civilian life in order to proceed.) There is no written standard for such a judgment, nor could there be; it must be made case by case. In 2006, the Army Counterinsurgency Field Manual, redrafted under the guidance of General David Petraeus, offers some elaboration. “Combatants cannot intend to harm noncombatants, though proportionality permits them to act knowing some noncombatants may be harmed,” the manual explains. “In policing situations, combatants cannot act in any way in which they know bystanders may be harmed.” Proportionality requires that soldiers discriminate between combatants and civilians—an especially difficult thing to do in a counterinsurgency, when threats quickly emerge and recede from the fabric of daily life.

Positive identification. All soldiers must “positively identify” a person whom they intend to kill as a legitimate combatant. According to the Rules of Engagement, this means that there must be a “reasonable certainty” that the person is displaying hostile intent, or is behaving in a hostile manner, before soldiers may attack. (In rarer circumstances, people can also be killed based on their “status”—that is, based on their affiliation with an organization that the military regards to be hostile—though this does not appear to be the case here.) One cannot determine the proportionality of a military operation without first positively identifying the combatants involved.

Command culture. The authority to use lethal force might rest with a person who is not at the scene of the battle, and so communication up and down the chain of command often plays a vital role in determining when soldiers can fire. On several occasions, the soldiers in the Apache seem to regard the conditions on the ground in the most threatening terms, even when there is limited evidence that this is so. “Have five to six individuals with AK-47s,” they tell the on-scene commander, after identifying only one or two armed people on the street. When the Apache is flying over Saeed Chmargh, while he is wounded and struggling on the pavement, the crew expresses hope that he’ll find a weapon so that they can kill him legally under the Rules of Engagement. But when the van arrives, the Apache crew reports to the commander, “We have individuals going to the scene, looks like possibly uh picking up bodies and weapons.” This is later amended to, simply, “picking up the bodies.” (There are important legal distinctions between the two scenarios.) Later, when requesting permission to fire a Hellfire missile into a building on a crowded street, Crazy Horse 1-8 tells the commander that there are “at least six individuals in that building with weapons” and that they are from a “previous engagement.” But there is also evidence that people without weapons are in the building, after a couple of seemingly unarmed men walk into it. At some point, when contradictory information is relayed, one would expect the commander to stop and ask for more details before granting the authority to demolish a building in a crowded area. The use of a Hellfire missile typically requires a probing collateral-damage assessment.