Army
They are used to defend their country, or attack another country's army. It is difficult, and a soldier must be in good shape, both physically and mentally. They almost always move together, and that way the team can do more things, in a safer way. They may be assigned to certain places to guard, or they may be told to search a place, or even attack it. That is up to their commander. Every soldier answers to someone else, so that way, everything is organized.