Each branch of the military sets an AFQT score requirement for applicants. The lowest qualifying score is 31, which is needed to join the Army. Higher scores are required for other branches of the military. For example, the Coast Guard only considers applicants with a score of 40 or more. Prospective recruits who have a GED rather than a high school diploma will, in most cases, need to score at least 50 on the AFQT.
The ASVAB is a series of tests developed by the Department of Defense and is used by the U.S. Army to determine whether you have the mental aptitude to enlist. The ASVAB also helps determine which Military Occupational Specialties (MOS) you qualify for. The ASVAB is required to enlist in the U.S. Army and is valid for two years. The ASVAB may be given in a computerized version at a Military Entrance Processing Station (MEPS) or in a paper version at various Military Entrance Test (MET) sites around the country or at high schools and colleges. 
The ASVAB Career Exploration Program (CEP) , takes approximately three hours, covers eight subjects and is composed of 200 questions. The ASVAB CEP is currently a pen and paper test. If it is offered by their school, high school students can take the ASVAB CEP test in grades 10, 11 and 12. They can only take it at the high school they attend, unless special arrangements are made.
The four most important sections of the test—Word Knowledge, Paragraph Comprehension, Arithmetic Reasoning, and Mathematics Knowledge-make up your Armed Forces Qualifications Test (AFQT) score. Your AFQT score ranges from 0 to 100 and determines if you are able to enlist in the military and which jobs and programs you may qualify for when you are in.

These scores include your Armed Forces Qualification Test (AFQT) score as well as your scores on each of the 9 individual subtests that make up the ASVAB.  When you get your report, the most important score you will want to look for first is your AFQT score.  This score determines your eligibility to serve in the military and to enlist in the U.S. Marines you need to have achieved a score of at least 32.
The next requirement comes as a fairly basic need for the military to identify possible threats it may be called upon to face. For this purpose, some of the commanding forces and other military, as well as often civilian personnel participate in identification of these threats. This is at once an organisation, a system and a process collectively called military intelligence (MI).
Test scores provide only one measure of your skills and abilities.  Test scores and grades, combined with information about your interests, values, skills, and achievements may help you select appropriate occupations for career exploration.  As you explore careers, you can compare your skills with the skill requirements of occupations in which you are interested.

As a general rule of thumb, anything over an 85 on the ASVAB will qualify you for nearly any position in the armed forces. But there are slight breakdowns within each score. For example, in order to qualify for Surveillance and Communications (SC) in the Army, Word Knowledge, Paragraph Comprehension, Arithmetic Reasoning, Auto & Shop and Mechanical Comprehension all require high marks. Though scoring an 85 or above would guarantee you scored in a high enough percentile to qualify for SC.
The exam is not a “pass or fail” test. Your score in each area reflects your own unique abilities. Of course, you will want to study with the aim of doing your best so that you can qualify for a job that fits your skills and career interests. Your AFQT score is compared to the scores of other recruits in the 18-23 year age bracket to see how your potential measures up.
A military or an armed force is a professional organization formally authorized by a sovereign state to use lethal or deadly force and weapons to support the interests of the state. It typically consists of branches such as an Army, Navy, Air Force, and in certain countries the Marines and Coast Guard. The task of the military is usually defined as defense of the state, and its citizens, and the prosecution of war against another state. The military may also have additional sanctioned and non-sanctioned functions within a society, including, the promotion of a political agenda, protecting corporate economic interests, internal population control, construction, emergency services, social ceremonies, and guarding important areas. The military may also function as a discrete subculture within a larger civil society, through the development of separate infrastructures, which may include housing, schools, utilities, logistics, health and medical, law, food production, finance and banking.
Direct commission: civilians who have special skills that are critical to sustaining military operations and supporting troops may receive direct commissions. These officers occupy leadership positions in law, medicine, dentistry, pharmacy, intelligence, supply-logistics-transportation, engineering, public affairs, chaplain, oceanography and others.
The Armed Services Vocational Aptitude Battery (ASVAB test--also known as the AFQT (Armed Forces Qualification Test). This is the score used by the recruiter to determine a potential recruit’s enlistment eligibility, assign a recruit to a military jobs, and aid students in career exploration. The AFQT is actually a subset of the ASVAB - only with scores of four of the ten test sections calculated.
Figure out which areas to focus on based on your career goals. If you’re not interested in a job requiring a score on the Mechanical Comprehension subtest, you don’t need to worry about doing well on that subtest. If you don’t need to worry about mechanics, don’t bother preparing for that section. Spend the time on Word Knowledge or Arithmetic Reasoning.
The President of the United States is the Commander in Chief, who is responsible for all final decisions. The Secretary of the Department of Defense (DoD) has control over the military and each branch - except the Coast Guard, which is under the Dept. of Homeland Security. With over 2 million civilian and military employees, the DoD is the world's largest "company."
Military history has a number of facets. One main facet is to learn from past accomplishments and mistakes, so as to more effectively wage war in the future. Another is to create a sense of military tradition, which is used to create cohesive military forces. Still, another may be to learn to prevent wars more effectively. Human knowledge about the military is largely based on both recorded and oral history of military conflicts (war), their participating armies and navies and, more recently, air forces.
Later this became known as military science, and later still, would adopt the scientific method approach to the conduct of military operations under the influence of the Industrial Revolution thinking. In his seminal book On War, the Prussian Major-General and leading expert on modern military strategy, Carl von Clausewitz defined military strategy as 'the employment of battles to gain the end of war'.[36] According to Clausewitz:

The questions that have a tendency to arise rather quickly are something along the lines of “why is this test so important?” and “What is the overall purpose of this test?” Well, first it is important to define the actual test and to assess the colorful history of the test. The Armed Services Vocational Aptitude Battery test (ASVAB) is a test that was officially formatted in 1968 with the intention of mentally preparing soldiers with knowledge that identifies with the following: