Each service has a uniformed head who is considered the highest-ranking officer within their respective service, with the exception of the chairman and vice chairman of the Joint Chiefs of Staff, and the chief of the National Guard Bureau. They are responsible for ensuring personnel readiness, policy, planning and training and equipping their respective military services for the combatant commanders to utilize. They also serve as senior military advisors to the President, the Secretary of Defense, their respective service secretaries, as well as other councils they may be called to serve on. They are as follows:
A major development in infantry tactics came with the increased use of trench warfare in the 19th and 20th centuries. This was mainly employed in World War I in the Gallipoli campaign, and the Western Front. Trench warfare often turned to a stalemate, only broken by a large loss of life, because, in order to attack an enemy entrenchment, soldiers had to run through an exposed 'no man's land' under heavy fire from their opposing entrenched enemy.
Under the Student Loan Repayment Program, when you enlist the Army will pay back up to $65,000 in qualified education loans (up to $20,000 for reservists), the Navy up to $65,000 and the Air Force up to $10,000. Each year 15% of the loan balance or $500, whichever is greater, will be repaid by SLRP. There may also be annual and cumulative caps on the amount repaid. Participants must score 50 or higher on the Armed Forces Qualifications Test (AFQT). SLRP must be requested at the time of enlistment or reenlistment. Qualified education loans include federal education loans such as the Perkins, Stafford, PLUS, or Consolidation loans, but not private alternative loans. Defaulted loans are not eligible. Payments made under the SLRP are considered taxable income.
Battlefield commission: under certain conditions, enlisted personnel who have skills that separate them from their peers can become officers by direct commissioning of a commander so authorized to grant them. This type of commission is rarely granted and is reserved only for the most exceptional enlisted personnel; it is done on an ad hoc basis, typically only in wartime. No direct battlefield commissions have been awarded since the Vietnam War. The Navy and Air Force do not employ this commissioning path.
The meaning of military tactics has changed over time; from the deployment and manoeuvring of entire land armies on the fields of ancient battles, and galley fleets; to modern use of small unit ambushes, encirclements, bombardment attacks, frontal assaults, air assaults, hit-and-run tactics used mainly by guerrilla forces, and, in some cases, suicide attacks on land and at sea. Evolution of aerial warfare introduced its own air combat tactics. Often, military deception, in the form of military camouflage or misdirection using decoys, is used to confuse the enemy as a tactic.
Personnel may be recruited or conscripted, depending on the system chosen by the state. Most military personnel are males; the minority proportion of female personnel varyies internationally (approximately 3% in India, 10% in the UK, 13% in Sweden, 16% in the US, and 27% in South Africa). While two-thirds of states now recruit or conscript only adults, as of 2017 50 states still relied partly on children under the age of 18 (usually aged 16 or 17) to staff their armed forces.
Military tactics concerns itself with the methods for engaging and defeating the enemy in direct combat. Military tactics are usually used by units over hours or days, and are focused on the specific, close proximity tasks and objectives of squadrons, companies, battalions, regiments, brigades, and divisions, and their naval and air force equivalents.
Note: While the U.S. Navy is older than the Marine Corps, the Marine Corps takes precedence due to previous inconsistencies in the Navy's birth date. The Marine Corps has recognized its observed birth date on a more consistent basis. The Second Continental Congress is considered to have established the Navy on 13 October 1775 by authorizing the purchase of ships, but did not actually pass the "Rules for the Regulation of the Navy of the United Colonies" until 27 November 1775. The Marine Corps was established by act of said Congress on 10 November 1775. The Navy did not officially recognize 13 October 1775 as its birth date until 1972, when then–Chief of Naval Operations Admiral Elmo Zumwalt authorized it to be observed as such.