One of the best examples of this dehumanizing of military members has to be the legions of ancient Rome. These soldiers were subject to much the same things that you listed; cut hair, similar uniforms, low privacy, and a highly ordered chain of command/subjection.

Heather P wrote a great explanation of the reasoning behind this in The Fall of the Roman Empire , Macmillan, 2005

• Roman military units of the period were largely homogeneous and highly regulated.

. In the legions of the Republic, discipline was fierce and training harsh, all intended to instill a group cohesion or esprit de corps that could bind the men together into effective fighting units. Unlike opponents such as the Gauls, who were fierce individual warriors, Roman military training concentrated on instilling teamwork and maintaining a level head over individual bravery − troops were to maintain exact formations in battle and "despise wild swinging blows" in favor of sheltering behind one's shield and delivering efficient stabs when an opponent made himself vulnerable.

Another example is something obtained from the Vindolanda Tablets, its reads;

...the commanding officer was addressed as domine ("master" or "lord", due to his equestrian rank) and soldiers of the same rank as frater ("brother") or collega ("comrade").

While its difficult to say where these methods were first developed, I can think of no better example than the army of ancient Rome considering that this ordering of its military contributed widely to its success and longevity.

These specific techniques of dehumanization have not so much changed over time as much as they have been refined to be considerably more effective. For example, the United States Armed Forces have spent quite a bit of money in order to polish and perfect this method, as well as break it down into steps of a process they refer to as "resocialization".

Confinement and suppression -

Once their training has begun, the right of recruits to leave the military estate (or to quit the armed forces) is denied or tightly restricted. By shaving the head, issuing uniforms, denying privacy, and prohibiting the use of first names, individuality is suppressed.

Control and conformity -

...recruits are conditioned to conform to military norms. In particular, recruits are repeatedly instructed to stand, march, and respond to orders in a ritual known as foot drill, which is derived from 18th-century military practices and trains recruits to obey orders without hesitation or question.

Stress and punishment -

The training process applies stressors continuously. Instructors may deprive recruits of sleep, food, or shelter; shout personal insults; use physical aggression; or give orders intended to humiliate. According to specialists in US recruit training, the conditions of continuous stress deplete recruits' resistance to the demands made of them.

Bonding -

As a buffer against the stressful conditions of their training, the trainee group normally forms a strong bond of mutual loyalty. Researchers in the US have described it as an intense "we-feeling", which can feel more powerful than the civilian bonds that recruits are familiar with. In 2006, an official report on Australian Defence Force training explained the importance of the group bond:

Willingness to apply lethal force requires… sufficient bonding within the team to override each individual’s natural human resistance to kill. The toughness and bonding required increases the closer the contact with the enemy.

Sources;

Vindolanda Tablets

Heather P., The Fall of the Roman Empire , Macmillan, 2005

John., Hockey, (1986). Squaddies : portrait of a subculture. Exeter, Devon: University of Exeter.

Bourne, Peter G. (1967-05-01). "Some Observations on the Psychosocial Phenomena Seen in Basic Training". Psychiatry.

McGurk; et al. (2006). 'Joining the ranks: The role of indoctrination in transforming civilians to service members', (in 'Military life: The psychology of serving in peace and combat [vol. 2]'). Westport: Praeger Security International.

Australia, Department of Defence (2006). "Final report of the Learning Culture Inquiry"

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