The Split Training Option or STO or "Split-Op," as it is often referred to, is an enlistment option available for the US Army Reserve and Army National Guard recruits. This program allows individuals to attend Basic Training during one summer, then attend Advance Individual Training the next. This enlistment option is popular among high school students who want to enlist right away.
Video Split Training Option
U.S. Army Reserve
The US Army Reserve is the federal part-time military. Reservists are considered to be employees of the United States' government and receive federal benefits. Reservists work on a federal status at all times. Soldiers in the US Army Reserve will attend their drill or battle assembly with a reserve unit that corresponds with their future MOS, for example an STO soldier whose future MOS is a 31B or Military Police, will do their battle assembly with an MP unit.
Maps Split Training Option
Army National Guard
When working in the national guard, you are a state employee, and your commander in chief is not the president, but rather the governor of your state. Army National Guard soldiers receive both federal and state benefits. During a state emergency, the governor of your state can call you to assist. The President can also federalize troops for missions requiring additional forces. During the periods before basic training and between basic and AIT, National Guard STO Soldiers will attend a program called the Recruit Sustainment Program or RSP. This program prepares potential soldiers for the rigors of basic training. Soldiers returning from basic combat training will continue to train with the RSP unit until they ship to and complete AIT.
Similar programs
The U.S. Army is not the only branch that offers a split option. The U.S. Coast Guard has one as well with their reserve component. The program allows you to attend "Boot Camp" one summer at Coast Guard Training Center Cape May and then attend an A school the next at either Training Center Yorktown or Training Center Petaluma. As of 2014, this program is not offered due to force reduction.
Source of the article : Wikipedia