Sub-lieutenant

Sub-lieutenant is a military rank. It is normally a junior officer rank.

In many navies, a sub-lieutenant is a naval commissioned or subordinate officer, ranking below a lieutenant. In the Royal Navy (RN) the rank of sub-lieutenant is equivalent to the rank of lieutenant in the British Army and of flying officer in the Royal Air Force (RAF). An RN sub-lieutenant ranks above an Army second lieutenant or an RAF pilot officer.

In some armies, sub-lieutenant is the lowest officer rank. However in Brazil it is the highest non-commissioned rank, and in Spain it is the second highest non-commissioned rank.

The NATO rank code is OF-1 (senior).

History of naval rank
In the British Royal Navy, a passed midshipman awaiting promotion often elected to become a master's mate, normally an experienced petty officer who assisted the sailing master. Though formally the rating did not lead to promotion to lieutenant, master's mates were paid more than any other rating and were the only ratings allowed to command any sort of vessel. A midshipman who became a master's mate got an increase in pay from £1 13s 6d to £3 16s per month, but initially reduced his chances at a commission. Over time, however, service as a master's mate became a normal part of the path to a commission. The situation caused some confusion during the last part of the 18th century, when two parallel roles—master's mates trying to become masters, and former midshipmen working toward a commission—held the same title and responsibilities aboard ship.

By the first years of the 19th century, the prefix "master's" was dropped for passed midshipmen, to distinguish them from master's mates in the navigator's branch. In 1824 two further grades were also introduced, consisting of master's assistants and second-class volunteers. These corresponded to midshipmen and first-class volunteers respectively in the executive line. From this point, passed midshipmen had the rating master's mate, abbreviated as mate, and prospective masters had the rating master's assistant. These changes helped eliminate the confusion caused by the mingling of midshipmen in the navigator's branch.

In 1838 a Royal Commission, presided over by the Duke of Wellington, recommended the institution of the rank of mate as an official step between midshipman and lieutenant. In 1861 mate was abolished in favour of sub-lieutenant.

Acting sub-lieutenant
In 1955, the Royal Navy created the rank of acting sub-lieutenant. Unlike their substantive counterparts, acting sub-lieutenants are subordinate officers, as they hold their ranks by order and not by commission. Upon passing Fleet Board, acting sub-lieutenants were confirmed as sub-lieutenants and issued commissions backdated to the date when they were appointed acting sub-lieutenants. The rank of acting sub-lieutenants was abolished in the Royal Navy around 1993, and now exists only in the Royal Naval Reserve.

Before its abolition, the rank of acting sub-lieutenant in the Royal Navy corresponded with, but was junior to, the ranks of lieutenant (Army) and flying officer (RAF). This can be seen in print versions of STANAG 2116 edition 5 (1992).

In many Commonwealth navies (e.g. Canada and Australia) however, the rank of acting sub-lieutenants still exists as a commissioned rank equivalent to Second lieutenant, while the rank of sub-lieutenant is equivalent to that of an army lieutenant. As the term "acting" is a designation, both acting and substantive ranks should be orally addressed as "sub-lieutenant;" the full designation including "acting" should be used in written documents, however. Indeed, when someone is addressed as "Acting sub-lieutenant" it can be seen as a way of patronising an individual in a derogatory manner due to the emphasis of their "acting" rank.

The Royal New Zealand Navy follows the US precedent in titling its lowest commissioned officer ensign.

In the Royal Thai Army, Army Reserve Force Students who complete grade 5 and their B.D. are promoted to the rank of acting second lieutenant (ว่าที่ ร้อยตรี).

Modern practice
In the modern Royal Navy, those joining as graduates start as sub-lieutenants with non-graduates joining as midshipmen. Sub-lieutenants are confirmed in their rank and receive their commission parchments upon passing out of Britannia Royal Naval College.

The same is true in the Royal Canadian Navy, with all undergoing basic officer training as Naval Cadets, but upon graduation those who joined with a bachelor's degree receive an immediate promotion to Acting sub-lieutenant while those that do not retain their rank as Naval Cadet until such time as they finish more career-related training.

Rank insignia: armies
In France, a sub-lieutenant (sous-lieutenant) is the junior commissioned officer in the army or the air force. He wears a band in the colour of his corps (e.g. gold for infantry, silver for armoured cavalry, etc.). During the 18th century a rank of sous-lieutenant de vaisseau existed in the French Navy. It was the equivalent of the master's mate rank of the Royal Navy. It is now replaced by the rank of "first ensign" (enseigne de vaisseau de première classe).

In Argentina, a sub-lieutenant wears a single silver sun on each shoulder.

In Brazil, a sub-lieutenant, the most senior non-commissioned rank, wears a golden lozenge.

In Mexico, the sub-lieutenant is the junior officer in the rank scale, wearing a single gold bar.

In Thailand, a sub-lieutenant and acting sub-lieutenant wears a single star on each shoulder.

Rank insignia: naval
In the Royal Navy, the Royal Australian Navy and the Royal New Zealand Navy, the insignia of both sub-lieutenants and acting sub-lieutenants consists of one medium gold braid stripe with an executive curl. The size of this stripe should not be confused with the narrow stripe, colloquially referred to as "spaghetti strap," used on the Royal New Zealand Navy rank of ensign and the Royal Canadian Navy's naval cadets. The Royal Air Force also followed this example of braiding when developing their rank system (see flying officer).

The insignia of sub-lieutenants in most commonwealth countries are identical to the United States Navy and United States Coast Guard grade of ensign (although US ranks do not use the executive curl), even though its equivalent grade in the USN is actually lieutenant junior grade.

In the Royal Canadian Navy, acting sub-lieutenants display one medium stripe. A sub-lieutenant adds a narrow stripe below the medium stripe to maintain the executive curl on the top. The equivalent army and air force second lieutenant rank has the narrow stripe above the medium stripe, since these elements do not need to maintain spacing on top due to the lack of an executive curl; the RCN followed this pattern before the addition of the curl in 2011.

British Army
The British Army briefly had a rank of sub-lieutenant in the late 19th century, replacing the ranks of ensign in the infantry and cornet in the cavalry. After a few years, it was replaced in turn by the rank of second lieutenant.