Box pleating is the older form, and no it is not just for military use.

In brief:

When the kilts were first tailored (in the last decade of the eighteenth century), they were box pleated from about 4 yards of cloth. The box peats were relatively wide and were "true" boxes -- that is, no or litte overlap of the cloth on the inside. Military and civilian kilts were pleated this way, military kilts to stripe and civilian kilts to no pattern. By 1820 or so, civilian kilts were also pleated to the stripe.

The first regiment to go to knife pleating was the Gordons, in 1854 (I think that date is correct, it was in the 1850s). By this time the yardage used in the kilt had started to increase (though not to today's 8 yards, probably closer to 5 or 6). With the exess cloth, the box pleated kitls also started to go with narrower pleats, meaning one side of the "box" was much deeper than the other.

By the time you get to the end of the nineteenth century, you have the kilt as we have it today -- about 8 yards of cloth, with knife pleating being the norm. Pleating to the sett was just starting to become the fashion.

Of course, when you get into the twentieth century, pleating to sett would become the norm, though pleating to stripe is still relatively common. The traditional four-yard box pleated kilts pretty much died out until kilt maker and kitl historian Bob Martin revived them in 1983. Since then a few other kilt makers (such as myself) have taken up making them, but they still are not nearly as common as the eight-yard knife pleated kilt we all know and love.

Aye,
Matt