Military ranks are a system of hierarchical relationships within armed forces, police, intelligence agencies and other institutions organized along military lines. Responsibility for personnel, equipment and missions grows with each advancement. The military rank system defines dominance, authority and responsibility within a military hierarchy. It incorporates the principles of exercising power and authority into the military chain of command—the succession of commanders superior to subordinates through which command is exercised. The military chain of command is an important component for organized collective action.

Uniforms denote the bearer's rank by particular insignia affixed to the uniforms of a number of countries. Ranking systems have been known for most of military history to be advantageous for military operations, in particular with regards to logistics, command, and coordination. As time went on and military operations became larger and more complex, more ranks were created and the systems of ranking became more complex.

Rank is not only used to designate leadership, but to establish pay-grade as well. As rank increases, pay-grade follows, but so does the amount of responsibility.

In modern armed forces, the use of ranks is almost universal. Communist states have, on several occasions, abolished the use of ranks (e.g., the Soviet Red Army 1918–1935, the Chinese People's Liberation Army 1965–1988, and the Albanian People's Army 1966–1991), but they have had to re-establish them after encountering operational difficulties in command and control.

From 501 BC, the Athenians annually elected ten individuals to the rank of strategos, one for each of the ten "tribes" that had been created with the founding of the democracy. Strategos means "army leader" and is usually translated as "general". Originally these generals worked together with the old polemarchos ("warlord") but over time the latter figure was absorbed into the generalship: each of the ten generals would rotate as polemarch for one day, and during this day his vote would serve as tie-breaker if necessary.

As an elected official a Strategos is by definition not a military rank. Strategos is a Political Rank in a Hierarchical Position above the military, politically similar in nature to a modern-day Sheriff or Police Commissioner. This is completely different from a modern day Commissioned Military General who never stands for election at any point in their careers. Historically it is unclear whether there was any badge of office granted to a Strategos though given current customs one should suspect that there was such a badge of office.

The confusion regarding the "Ranking" of Strategos surely stems from the modern custom of granting Police Commissioners and Sheriff's, both Political Ranks, a badge-of-office that happens to be in the shape of what is commonly understood to be a very high rank within the traditional military hierarchy. This "rank-shaped" badge-of-office a formal representation of Public Civilian (political) authority over military matters.

The ten generals were equal to one another; there was no hierarchy among them. However, a basic form of democracy was in effect: for example, at the Battle of Marathon in 490 BC, the generals determined the battle plan by majority vote. Particular assignments might have been given to individual generals; inevitably there was a regular division of responsibilities.