CIA. KGB. MSS. All acronyms that anyone familiar with the intelligence world would know. (For those who may not be familiar, they stand for: Central Intelligence Agency — United States, Komitet Gosudarstvennoy Bezopasnosti — Soviet Union/Russia, and the Ministry for State Security — China). They are all well-represented in the modern media.

But what about the lesser-known, more obscure intelligence apparatuses out there and throughout history? Some had a definitive intel mission, while others were more of a “grey area.” But they all served the purpose of providing commanders and policymakers with a clear picture of a given situation.

This is the first of a series of articles that will introduce and discuss these units, from ancient to modern times.

Biblical Spies

The gathering of intelligence for tactical, strategic, and political purposes dates back to biblical times. According to the Old Testament (Joshua 2), in preparation for an attack on the city of Jericho: “Then Joshua son of Nun secretly sent two spies from Shittim. ‘Go, look over the land,’ he said, ‘especially Jericho.’ So they went and entered the house of a prostitute named Rahab and stayed there.”

According to the text, Rahab hid the spies from the soldiers who were searching for them, then gave them instructions for escape. They were able to gather the information needed and report back to Joshua. The attack on Jericho was ultimately a success. Typical of the day, there were no dedicated intel units. Instead, men were handpicked, usually based on their speed of foot and ability to blend in, by the military commander or king, and went out and gathered information on enemy strength, position, and morale.

In a biblical display of how intelligence gathering (or lack thereof) can change the course of a battle, in Joshua 10, Joshua, responding to the call of the Gibeonites for aid against the Amorites, marched his army all night. Upon reaching a lay-up point for his men to rest and eat, he sent out a reconnaissance unit to gather intel on the enemy’s position. Realizing from the unit’s reports that he had marched his men into the rear of the enemy positions, Joshua attacked. The Amorites, who in being so focused on laying siege to the Gibeonites, had failed to set rear security, and were routed.

Early Greek Spies and the Krypteia

According to Dr. John M. Nomikos, director of the Research Institute for European and American Studies, in classical Greek history, clandestine and covert ops were both common and hated methods of statecraft. No state would admit to the use of either, knowing that if the operations became public, it would be severely disapproved. Among other things, the Greeks used local citizens who served as “proxenoi.” They had to be a citizen of the city-state in which they served, but not of the city-state which they represented. These men became the equivalent of modern spies or agents. During the Peloponnesian War, they were a conduit for information and clandestine activities in the course of their normal duties.

The background and mission of the Spartan Krypteia, meaning “the hidden, secret things,” is the subject of much debate among historians. Some believe that they were a kind of secret police or state security force whose sole purpose was to terrorize the helot population — the servant-class of ancient Sparta. Others speculate that, at least on the battlefield, the krypteia were used as reconnaissance and special-operations forces, in addition to their role as intel officers.

Like something out of the movie The Purge, every autumn, the Spartan ephors (magistrates) would declare an informal war on the helots. For a period of time, any Spartan citizen could, without fear of punishment, kill a helot. The kryptes role in this was not only to kill but also to gather intelligence on any helot who was known or suspected of trying to incite rebellion and unrest.

The life of a kryptes was not for everyone. Only after successfully completing their training at the agoge — the state-controlled education system designed to impart fitness, obedience, and courage — were certain young men chosen for the krypteia program and given a chance at future leadership roles. They were given that chance once a year.

Only those Spartans who had successfully served in the krypteia could expect to serve in the upper ranks of the Spartan military and society, as it was believed that only those with the ability and willingness to kill for the state were worthy of such reward.

The Frumentarii

In a nod to modern-day “secret police,” such as Iran’s SAVAK and World War II Japan’s Kempeitai, the Frumentarii were officials of the ancient Roman state during the 2nd and 3rd centuries. Much of what is known about them comes from inscriptions found on gravestones and through anecdotes mentioned by historians. Originally, the Frumentarii were wheat collectors. They were attached to individual legions, and played an “overt” role as overseers of supplies and logistics, often working in uniform for easy identification on the battlefield.

Roman militaries had long resisted using organized units of informers and spies, but when the utility of the frumentarii was realized, they were placed into positions where they could be most effective. Candidates for the units were given special training. Evidence of this is found on inscriptions in the cities of Cordoba and Arles which read “frumentario canaliculario,” suggesting special knowledge of inland navigation. This came in handy when reporting on what all military commanders find at the top of their list when it comes to the enemy: geographic location.

Some scholars believe that the Antonine Itinerary, a register of the stations and distances along the various roads of the Roman empire, and which contained directions on how to get from one Roman settlement to another, might have been produced by the frumentarii. The frumentarii were also used extensively as spies against their own people, even amongst their own friends and families.

The formation of the frumentarii was the brainchild of Hadrian, the 14th Emperor of Rome. Hadrian realized that by virtue of their jobs as collectors of wheat in any given province, the frumentarii were in an optimal position to leverage their contact with locals and natives of occupied territories in order to collect needed intelligence. They could also act as a ready-made courier system.

As soon as their role for the Emperor was learned by the people of Rome, the frumentarii became hated. Association with the unit and its leaders would bring repercussions, and eventually, Emperor Diocletian disbanded the unit because of its abuses and reputation. However, they were soon resurrected in the form of the equally brutal, but better organized, agentes in rebus, or “those active in affairs.”

This article was originally published in 2014.