I'm researching a bit of family history based on information which I believe are from church records in Finland, however not having seen the records myself I can't be sure. What I have states that one of my ancestors (b. 1544 in present-day Savonia in Finland) was a footsoldier ("nihti" in Finnish, from "knekt" in swedish) from 1591 to 1604, and then a "knaapi" (väpnare/squire) from 1609, serving in the "troops of Jacob De La Gardie" and perishing in "a campaign in Russia" in 1610.
So my question is, what did these roles actually mean in terms of responsibility, rights, employment and status in Sweden? How did you become a soldier? What did it take to become a "väpnare" and what does that mean? Do these terms actually reflect military "rank" or social/economic status?
A follow-up question: Presuming that this information is correct, he was also quite old when doing this, 47-60 at his time as a soldier and a whopping 66 as a squire when he died in 1610. Is this plausible or is my information just likely to be incorrect? What was the typical military career like at the time, just in terms of age and possible promotions in status?
I think you have encountered a social climber in your family. Absolutely fascinating.
A knekt was a foot soldier, usually part of a fänika a company sized formation instituted as a part of a regular army by King Gustav I shortly after his victory against the Dacke rebellion 1543. It was an attempt to create a local version of the effective German landsknecht mercenary units. Each county would raise a certain number of fänikor that would garrison castles, help the taxmen collect taxes and in need go to war. Initially, they were designed more as a more permanent peasant militia to be filled out with peasant militia in case of war, but as time progressed, they became more and more like a regular army. They were however not of the same quality as the landsknechts used by the Danes in the Nordic 7 years war 1563-1570.
A group of farms would be granted a tax reduction for raising a knekt, which is probably how your ancestor became one - he might have been a crofter, a landless tradesman or a second or third son of a self-owning farmer that took on the role as knekt in order to supplement his income. He might have been a peasant himself seeking to reduce his tax burden, especially if he had an older son or younger brother who could help his family take care of the farm.
After the disastrous defeat at Kirkholm 1605, King Karl IX was desperate for cavalry and thus promised to ennoble anyone who could raise a horse and a cavalryman for his army in 1608. It seems likely your ancestor had been a successful soldier and/or peasant and could afford a horse and to take the offer and become a sven or väpnare (squire).
Sweden was at war with Poland-Lithuania at the time (thus the defeat at Kirkholm 1605), and when Poland-Lithuania got involved in the times of trouble in Russia, King Karl IX sent Jacob De La Gardie with a mixed army of Swedish troops and mercenary forces to support Vasilig IV of Russia's claim to the throne. De La Gardie's forces took Moscow, but were defeated by the Polish-Lithuanians and their Russian supporters at Klusjino 1610.
As per your original question - being a knekt in a fänika meant that a group of self-owning farmers (self-owning farmers owned roughly 40-50% of the arable land in Sweden at thsi time) provided you with equipment and pay and that you had a responsibility to go to war if the King called. If you were a crofter or otherwise landless person, this often meant an increase in status.
A sven or väpnare would be frälse, that is noble and extempt from tax, but required to serve in adelsfanan (the noble cavalry regiment) or other cavalry units when the King called. Even if you were of the lowest titleless nobility, you were still noble and at least theoretically part of the upper crust of society.
The age was usually irrelevant when soldiers were mustered and considered for service - their health and strength were inspected, but not their age. If your ancestor was hale and healthy and sound of body and mind, he could very well serve at an advanced age.
Later bookkeeping is much better than earlier, so I can't say for sure about the late 16th and early 17th century, but soldiers were stricken often for being "old and infiirm" or "old and incapable" in the late 17th century, but I have not encountered "old" as the single reason for striking a soldier from service.