This is how it is used by people around me here in central Canada. For example, “I was only driving 50 klicks over the speed limit when the copper flashed his lights, it took him 4 kays to catch up with me and boy was he mad.” 
“Klick” is easier to say, it’s only a one-syllable word, compared to “killo-meter” or “kil-LOM-met-ter.” You’ll hear “K” used as well (remember the 10-Kay zone around the Iron Curtain?), but a single consonant sound can be confused with so many OTHER single consonant sounds. That’s why the military has “Alfa, Bravo, Charlie, Delta” for the letters of the alphabet.
It’s been my observation that countries that actually USE the metric system call 'em “killo-meters,” while we stupid yay-who Yankees call 'em “kil-LOM-met-ters.”
Besides, you NEVER ask why the military does something. Sheesh, people!
~VOW
Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you!
Tripler
About damn time someone realized this. 
You know - if you all would have “listened” to yourselves.
Phonetic alphabet use says “kilo” - you wouldn’t WANT to also say kilo or kilometer. It would be too confusing over radio traffic. The one meter thing is true! Ranging on maps and on compasses are in kilometers. Early on, it was discovered that the metric system made more sense in certain measurements. A “click” on a site took the round a specific amount over or up. 1mm over at 1 meter does translate to 1 meter over at one kilometer! It’s a much more linear system than miles or feet!
Except that as was establish here already using click for kilometer started at least in the early 50s and possibly much later. The military was still using “king” for the letter k officially until the late 50s and unofficially until much later.
I learned long ago never to trust Bryson. He’s entertaining, but I wouldn’t use him as a primary reference.
I remember a song using the term ‘keys’, but it refered to kilograms, not kilometers:
Flying in a big airliner
Coming into Los Angelees
Bringing in a couple of keys
Don’t touch my bag if you please, Mr. Customs man.
Alternate spellings that are pronounced the same often indicate that the word emerged in spoken communications rather than written. Something like military talk, where the word should be short, and distinctly different from other words, even over noisy transmissions.
Joe Haldeman, a U.S. Army combat engineer during the Vietnam War, also often used “klicks” to refer to kilometers in his distant-future military sf novel The Forever War, published in 1974.
“bought the farm” is a lot older than Viet Nam or WWI - it refers to fraternal insurance where a death paid off the mortgage.
Do you have a definitive cite for that? As far as I know, the origins of this phrase are speculative. See here. Or here, unless more evidence has recently surfaced.
Give me a break, that was 14 years ago! 
I’ve long since come to the same conclusion as you.
Yes, but we’re looking for the first citation.
And one of that book’s many flaws is that it isn’t distant-future. It starts in the 1980s, which means that Haldeman was positing full manned exploration of the Solar System, a practical FTL drive, radical changes in military culture, and all the rest within a mere decade.
By the end, due to time dilation, it’s set several hundred years from now.
Ha, completely missed the dates on this one! I would have trusted Bryson 14 years ago, too!
No, it comes from the Bible. Acts ch1 V 17-19
Judas was one of us and had worked with us, but he brought the mob to arrest Jesus. 18 Then Judas bought some land with the money he was given for doing that evil thing. He fell headfirst into the field. His body burst open, and all his insides came out. 19 When the people of Jerusalem found out about this, they called the place Akeldama, which in the local language means “Field of Blood.”
NB I’m joking. This probably isn’t the origin. Someone has to invent these folk etymologies.
I did not remember any such reference in Troopers, and I just confirmed it with a text search on an etext. He does NOT use the term.
From back in my doper (not THAT doper) days, I knew it a shorthand for microgram, one millionth of a gram.
In the US military “mike” is short for minutes. I’ve never heard anything else.
Here is a cite that goes back to 1960.
“Mike” is just short for the letter “M”, and so can stand for anything the letter can stand for.
I just reread 'Starship Troopers", and I was certain it was in there.
So I also did a text search, and yes, you are right. No “klicks” or “clicks” for units of distance.
But the verb “click” sure gets used a lot, so I can see the source of confusion. He has his own slang term “click” for activating a communication channel. (And that’s without all the clicking heels and stuff- I thought that they were cloggers after I did my search.)