In Medieval Europe, tales of knighthood and chivalry, the officer class of the period captured the popular imagination. Writers and poets like Taliesin, Chrétien de Troyes and Thomas Malory wrote tales of derring-do, featuring Arthur, Guinevere, Lancelot and Galahad. Even in the 21st century, books and films about the Arthurian legend and the Holy Grail continue to appear.
One of the oldest military publications is The Art of War, by the Chinese philosopher Sun Tzu. Written in the 6th century BCE, the 13-chapter book is intended as military instruction, and not as military theory, but has had a huge influence on Asian military doctrine, and from the late 19th century, on European and United States military planning. It has even been used to formulate business tactics, and can even be applied in social and political areas.[where?]
After enlistment, new recruits undergo basic training (also known as "boot camp" in the Marine Corps, Navy and Coast Guard), followed by schooling in their primary Military Occupational Specialty (MOS), rating and Air Force Specialty Code (AFSC) at any of the numerous training facilities around the United States. Each branch conducts basic training differently. The Marine Corps send all non-infantry MOS's to an infantry skills course known as Marine Combat Training prior to their technical schools. Air Force Basic Military Training graduates attend Technical Training and are awarded their Air Force Specialty Code (AFSC) at the apprentice (3) skill level. All Army recruits undergo Basic Combat Training (BCT), followed by Advanced Individual Training (AIT), with the exceptions of cavalry scouts, infantry, armor, combat engineers and military police recruits who go to One Station Unit Training (OSUT), which combines BCT and AIT. The Navy sends its recruits to Recruit Training and then to "A" schools to earn a rating. The Coast Guard's recruits attend basic training and follow with an "A" school to earn a rating.
While considered part of the non-commissioned officer corps by law, senior non-commissioned officers (SNCOs) referred to as chief petty officers in the Navy and Coast Guard, or staff non-commissioned officers in the Marine Corps, perform duties more focused on leadership rather than technical expertise. Promotion to the SNCO ranks, E-7 through E-9 (E-6 through E-9 in the Marine Corps) is highly competitive. Personnel totals at the pay grades of E-8 and E-9 are limited by federal law to 2.5 percent and 1 percent of a service's enlisted force, respectively. SNCOs act as leaders of small units and as staff. Some SNCOs manage programs at headquarters level and a select few wield responsibility at the highest levels of the military structure. Most unit commanders have a SNCO as an enlisted advisor. All SNCOs are expected to mentor junior commissioned officers as well as the enlisted in their duty sections. The typical enlistee can expect to attain SNCO rank after 10 to 16 years of service.