The Antipodean wrote to ask why the army contains many majors and no minors. This ignores child soldiers, but is a good excuse for running from the bottom brass through to the top.
The modern ranks were only arranged a few hundred years ago. This means that many of the etymologies make no sense at all. Heads outrank horse-servants, and biggers are smaller.
A corporal has nothing to do with corporal punishment. He comes, via caporale and capo, from caput, the Latin for head*. This is odd as a corporal is the lowest and least of non-commissioned officers.
A sergeant is simply a servant, and is therefore superior to the head.
A lieu-tenant is simply French for a place-holder, or a substitute. The idea is that if I can't be present in person I can send a somebody to take my place and to act with my authority. American lieutenants are loo-tenants, because they're incontinent. English lieutenants are left-tenants, because they're all socialist. French lieutenants have women.
A captain, like corporal, derives from the Latin caput, meaning head.
Major is Latin for bigger. A major was originally a shortening of sergeant-major or bigger servant and his rank has been steadily rising. In Catch-22 a chap whose name is Major Major Major is promoted to the rank of major through an administrative error: thus becoming Major Major Major Major.
A colonel is, literally, a colonnade. A colonnade is a line of columns and a colonel is the chap marching at the head of a column. In a nutshell, colonels have nothing to do with kernels, and there is no truth in them.
Generals are, in general, the general head of the army. It is a shortening of captain general, which was formed along the same lines as attorney general and Estates General and other post-positive adjectives. Generals are therefore generic and genetic, ruling over a genus of soldiers.
I have always wilfully misunderstood Hamlet's line about a play being "caviar to the general" as referring to a gourmandising soldier. The phrase actually means that, just as caviar is disliked by the general public, but loved by gourmets, so the play he refers to is unpopular with the hoi polloi, but appreciated by those who know about such things. I am certain that Shakespeare must have used the phrase himself, before giving it to Hamlet.
Fields Marshals are not, etymologically, martial. Martial comes from Mars, the god of war and relates to martians. Marshals, on the other hand, are mare-skalkaz or horse-servants. Thus putting them, etymologically, below corporals, which shows how logical the army is. It also makes Marshall Ney's name even more amusing.
And soldiers themselves: the word derives, as I have already mentioned, from salt. This means that, if you're an officer, you have salty privates.
Incidentally, what do you get if you drop a grand piano on a barracks?
A flat major.
Now repeat with a pit-shaft.
*Although some say that the reverse is true.