When I joined the army a long time ago, I was the regular teenager with my face barely visible behind my long, wavy, bathed in gel hair. The first day of training, I was taken to the barber shop where my lovely tresses were ruthlessly and mercilessly trimmed, leaving me with just a centimetre of hair in a small square patch at the centre of my head. It was traumatising to say the least, plus while the rest of my body was safely ensconced in warm clothes, my head was cold with the wind actually touching my scalp for the first time since I started going to the barber unaccompanied by my parents. Eventually I got used to it and today even though nobody expects me to keep my hair that short, I still get a haircut every week.
Now i realise, like everything else in the army the "funny" haircut has its logic as well.
1. It is a sort of rite of passage. People come to the army from different backgrounds, cultures and economic conditions. The army doesn't require Rambos. The army wants people who can work effectively as a team. The haircut is the first step in telling a fresh group of recruits that you no longer have your individual identity(at least till the training is over). This is followed by a barrage of other methods to break you down mentally and strip you of any sense of self worth(a la the drill sergeants, all powerful seniors, constant shouting, breaking down your sleep cycle etc). The haircut makes you indistinguishable among your peers and ultimately you end up a machine that only follows orders. At some point of time things start getting better. You start earning privileges as you become senior, your sense of self worth increases and by the time you pass out you are a finely honed war machine(at least you believe so) who has actually earned his self confidence and pride.
2. Hygiene is another main factor. You are going to be in very close proximity of your fellow trainees for an extended period of time and you wouldn't want to transfer lice and other scalp ailments to each other. Plus, you are going to be in situations where you may not get to bathe for long periods of time, you are going to be rolling in the murkiest and dirtiest of pools and I can assure you having a mane like Carlos Puyol will ensure your scalp turns into an ecosystem teeming with a wide variety of undesirable wildlife . Short hair is easy to manage, in fact it doesn't have to be managed.
3. It looks smarter. Imagine a soldier all neatly turned out, his brass buttons shining, his shoe polished like a mirror, his hair neatly tucked in a ponytail under his beret.... wait did I just say ponytail.
PS: Not just men, women crop their hair as well during military training.
Source: Kiren (Quora)
