As a nation state, Italy has emerged only in 1871. Until then the country was politically divided into a large number of independant cities, provinces and islands. The currently available evidences point out to a dominant Etruscan, Greek and Roman cultural influence on today's Italians.
It appears the LDS do not have military records for this area on microfilm. 17 was the age they were drafted during my grandfathers time according to his stories and my cousins grandfather's stories. There is a military archive you can request the "lista di leva" from. I think there is one located in each province. Sorry I can't be more help.
From this, find the state archives that corresponds with Avelino. I sent away for these (lista di leva) just a few months ago for Benevento and Reggio Calabria. I just e-mailed the appropriate state archives in Italian. Include the name, birth date and town of birth of the person you are looking for and include your address in the request. They will then tell you if there is a charge. Luckily, there was no charge for BN and RG records. They replied to my e-mail in about 3 weeks and then about 2 weeks later, I got the papers from them.