Military objectives are combatants and those objects which, by their nature, location, purpose or use, effectively contribute to the enemy’s war-fighting or war-sustaining capability and whose total or partial destruction, capture, or neutralization would constitute a definite military advantage to the attacker under the circumstances at the time of the attack. Military advantage may involve a variety of considerations, including the security of the attacking forces. 

Proper economic targets for naval attack include enemy lines of communication used for military purposes, rail yards, bridges, rolling stock, barges, lighters, industrial installations producing war-fighting products, and power generation plants. Economic targets of the enemy that indirectly but effectively support and sustain the enemy’s war-fighting capability may also be attacked. 

Deliberate use of noncombatants to shield military objectives from enemy attack is prohibited. The presence of non-combatants within or near military objectives does not preclude an attack on such objectives … Unlike military personnel (other than those in a specially protected status such as medical personnel and the sick and wounded) who are always subject to attack, whether on duty or in a leave capacity, civilians are immune from attack unless they are engaged in direct support of the enemy’s armed forces or provide them with logistical support. Civilians who provide command, administrative or logistical support to military operations are exposed to attacks while performing such duties. Similarly, civilian employees of navy shipyards, the merchant navy personnel working on ships carrying military cargo, and the workers on military fortifications can be attacked while they carry out such activities.