All of the branches work together during operations and joint missions in Unified Combatant Commands, under the authority of the Secretary of Defense with the typical exception of the Coast Guard. Each of the Unified Combatant Commands is headed by a Combatant Commander, a senior commissioned officer who exercises supreme command authority per 10 U.S.C. § 164 over all of the forces, regardless of branch, within his geographical or functional command. By statute, the chain of command flows from the President to the Secretary of Defense to each of the Combatant Commanders.[20] In practice, the Chairman of the Joint Chiefs of Staff often acts as an intermediary between the Secretary of Defense and the Combatant Commanders.
The Air Force ASVAB scores are frequently a subject of confusion and anxiety for the person planning a career in the Air Force. The real meaning of ASVAB scores as they apply to each person's future in this branch of the military is rarely explained fully . There are some unfortunate misapprehensions about what the scores mean and how they affect a person's occupational prospects in the Air Force.

There are several different authorized pay grade advancement requirements in each junior-enlisted rank category (E-1 to E-3), which differ by service. Enlistees in the Army can attain the initial pay grade of E-4 (specialist) with a four-year degree, but the highest initial pay grade is usually E-3 (members of the Army Band program can expect to enter service at the grade of E-4). Promotion through the junior enlisted ranks occurs after serving for a specified number of years (which can be waived by the soldier's chain of command), a specified level of technical proficiency or maintenance of good conduct. Promotion can be denied with reason.
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.
Just as the President, the Secretary of Defense, and the Secretary of Homeland Security, are in charge of the entire military establishment, maintaining civilian control of the military, so too are each of the Defense Department's constitutive military departments headed by civilians. The four DoD branches are organized into three departments, each with civilian heads. The Department of the Army is headed by the Secretary of the Army, the Department of the Navy is headed by the Secretary of the Navy and the Department of the Air Force is headed by the Secretary of the Air Force. The Marine Corps is organized under the Department of the Navy, however it is still considered a separate and equal service. The Coast Guard is under the Department of Homeland Security and receives its operational orders from the Secretary of Homeland Security. However, the Coast Guard may be transferred to the Department of the Navy by the President or Congress during a time of war, thereby placing it within the DoD.[17]

On 3 December 2015, U.S. Defense Secretary Ashton Carter announced that all military combat jobs would become available to women.[38] This gave women access to the roughly 10% of military jobs which were previously closed off due to their combat nature.[39] The decision gave military services until January 2016 to seek exceptions to the rule if they believe that certain jobs, such as machine gunners, should be restricted to men only.[40] These restrictions were due in part to prior studies which stated that mixed gender units are less capable in combat.[41] Physical requirements for all jobs remained unchanged, though.[41] Many women believe this will allow for them to improve their positions in the military, since most high-ranking officers start in combat positions. Since women are now available to work in any position in the military, female entry into the draft has been proposed.[42]

Under the Montgomery GI Bill, the Army, Navy, Air Force, Marine Corps and Coast Guard (and their Reserves and the National Guard) provide a cash education incentive to encourage you to join and serve a tour of duty. The Montgomery GI Bill (MGIB) provides up to 36 months of education benefits to eligible veterans for college, business, technical or vocational courses, correspondence courses, apprenticeship/job training and flight training. MGIB benefits may be used while on active duty or after a fully honorable discharge from active duty.

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,[8] 10% in the UK,[9] 13% in Sweden,[10] 16% in the US,[11] and 27% in South Africa[12]). 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.[13]
The First World War was also responsible for a new kind of military depiction, through poetry. Hitherto, poetry had been used mostly to glorify or sanctify war. The Charge of the Light Brigade by Alfred, Lord Tennyson, with its galloping hoofbeat rhythm, is a prime late Victorian example of this, though Rudyard Kipling had written a scathing reply, The Last of the Light Brigade, criticising the poverty in which many Light Brigade veterans found themselves in old age. Instead, the new wave of poetry, from the war poets, was written from the point of view of the disenchanted trench soldier.
The IRT model underlying ASVAB scoring is the three-parameter logistic (3PL) model. The 3PL model represents the probability that an examinee at a given level of ability will respond correctly to an individual item with given characteristics. Specifically, the item characteristics represented in the 3PL model are difficulty, discrimination (i.e., how well the item discriminates among examinees of differing levels of ability), and guessing (i.e., the likelihood that a very low ability examinee would respond correctly simply by guessing).