Eli5: why does the military make everyone move every few years?

There are at least a couple of reasons that it’s useful to a military force to keep shuffling people around.

1. Any military force is going to benefit from diversity of training, and one of the ways you get that is by moving people into new circumstances. There’s a lot to unpack, but what they ideally want is a lot of people with a lot of different experiences, as opposed to a lot of entrenched specialists with deep but narrow skillsets.

Especially because they don’t want to find themselves in situations where certain jobs are dependent on specific people to do them – “Joe has been running these machines for so long that he’s really the only one who understands the system.”

That’s bad for any business of course, but all risks in the military are magnified by the fact that not only are lives at stake, but your nation’s entire way of life can be hanging in the balance.

And 2) they can’t guarantee that the workers will stay. People enlist for a period of time, and then they may decide not to continue. They need to be able to be easily replaced with another worker who can be slotted into that position with as little loss of functionality to the unit as possible.

One interesting reason is that it helps prevent loyalty to any single commanding officer or unit.

You don’t want military to be loyal to any specific person*, only to the country, so moving leadership around every once in a while prevents officers from “empire building”.

• you do swear allegiance to the commander in chief but it’s a bit nuanced.

What the others mentioned is correct.

However, in general they are not ”getting retrained.” Everyone in the .mil has a specific career track. Even though you may move as part of a promotion, every person at a given level in that career track is supposed (although this doesn’t always work) have the same skills and knowledge.

To make a very simple analogy, you replace a 60 watt lightbulb with a 60 wat lightbulb.

You don’t get a whole new job when you PCS. If you were a Mortarman in the 82nd Airborne at Fort Liberty and you PCS to Fort Riley, you’re still a Mortarman. Your new unit will do things differently because they have a different mission focus/SOPs, but your job is still put the mortar in the tube and drop pain on the bad guys.

And there’s a huge benefit to the cross-training, you make more well-rounded soldiers. For better and worse, organizations have their own culture. Ideally, what happens when you have someone leave they’ll take the good parts of their old unit’s culture to their new unit and make that unit better.

Because the standard contract for enlistment is usually about 4 years. Some people go into the military for a career, many others go in to do 4 years’ service and get their college paid for. The latter leave job vacancies when they leave, and a class of new recruits may not have everything they need to cover (plus, the people who just left were probably a few ranks higher than someone right out of basic).

Plus, military operations are changing constantly, depending on hundreds of factors, and so personnel need to shift to meet needs.