The decision-making method that would be used in this situation is consensus.
Consensus method is a group decision-making method. When a group chooses this method, all the members of this group participate in the process of making a decision about a specific issue. After discussing it thoroughly, they reach an agreement that fits the group's common goal. The method most likely to be used in the situation described is consensus because the military platoon would take a decision after hearing everyone's opinion, always focused on the common goal: defending their lives from the enemy.