The years since the fall of the One Sith have seen a relatively peaceful time in the galaxy. It has been nearly 40 years, and with the exception of a few rebellions and planetary political clashes, the Triumvirate has held true to its peace accords. But all good things must come to an end.
The need for localized militia was beneficial to both the Triumvirate and the systems that needed a military force to help with minor conflicts; this led to many mercenary guilds cropping up across the galaxy.