Military Officer -- a Profession Like No Other
Commissioned officers are referred to as such becuase they receive a commissioning warrant from the President of the United States who, "reposing special trust and confidence in the patriotism, valor, fidelity and abilities..." directly commissions the officer to serve in a branch of the US military. An officer generally follows a few different paths to obtaining his commission, either through one of the service academies, a Reserve Officer Training Corps (ROTC) program, or by attending one of the branch's Officer Candidate School (OCS). The officer will receive his commission upon successful completion of this initial training and receiving their degree from a four-year university and then continue on to more advanced training in his particular career specialty, whether that be infantry, intelligence, logistics, pilot or many other specialties.
However, while the officer is expected to be knowledgable and proficient in his speciality, their job is different becuase it places more emphasis on leadership and mission accomplishment, as a new officer can be placed in charge of anywhere from 4-50 subordinates when they first take command. Thus, the officer is held accountable for the training and development of those under their command and is ultimately responsible for what is, or is not, accomplished.